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Fractional integration analysis of precipitation dynamics: empirical insights from Nigeria Tellus A (IF 1.932) Pub Date : 2021-01-18 O.O. Awe; L.A. Gil-Alana
Abstract This paper deals with the time series analysis of precipitation patterns in Africa’s most populated nation using recently developed flexible modelling techniques to study the monthly precipitation data of some major economically viable and highly populated regions in Nigeria. The results indicate that there is a significant trend for Lagos rainfall data, implying that precipitations have systematically
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Bispectral analysis of nonlinear interaction, predictability and stochastic modelling with application to ENSO Tellus A (IF 1.932) Pub Date : 2021-01-07 Carlos A. L. Pires; Abdel Hannachi
Abstract Non-Gaussianity and nonlinearity have been shown to be ubiquitous characteristics of El Niño Southern Oscillation (ENSO) with implication on predictability, modelling, and assessment of extremes. These topics are investigated through the analysis of third-order statistics of El Niño 3.4 index in the period 1870–2018, namely bicovariance and bispectrum. Likewise, the spectral decomposition
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Some quantitative characteristics of error covariance for Kalman filters Tellus A (IF 1.932) Pub Date : 2020-12-30 Wei Kang; Liang Xu
Abstract Some quantitative characteristics of error covariance are studied for linear Kalman filters. These quantitative characteristics include the peak value and location in the matrix, the decay rate from peak to bottom, and some algebraic constraints of the elements in the covariance matrix. We mathematically prove a matrix upper bound and its quantitative characteristics for the error covariance
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On the diurnal cycle and variability of winds in the lower planetary boundary layer: evaluation of regional reanalyses and hindcasts Tellus A (IF 1.932) Pub Date : 2020-12-30 Ronny Petrik; Beate Geyer; Burkhardt Rockel
Abstract To accurately calculate the impact of renewables on power production in complex electric power grids, high-resolution and ideally seamless data within the planetary boundary layer are required. Therefore, the quality of different regional reanalyses and hindcasts is evaluated with respect to the representation of the planetery boundary layer and related sub-daily processes. On the one hand
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A preliminary assessment of the value and impact of multiple configurations of constellations of EON-MW, a proposed 12U microwave sounder CubeSat for global NWP Tellus A (IF 1.932) Pub Date : 2020-12-17 Yan Zhou; Narges Shahroudi; Tong Zhu; Flavio Iturbide-Sanchez; Eric S. Maddy; Sid-Ahmed Boukabara; Kayo Ide; Ross N. Hoffman
Abstract Observing system assessments were made for the Earth Observing Nanosatellite-Microwave (EON-MW), a 12U CubeSat analog of the Advanced Technology Microwave Sounder (ATMS). Since the EON-MW channels and sensor specifications closely follow those of ATMS, the sensor characteristics and geophysical capabilities assessments indicate that the value of information for humidity (temperature) of EON-MW
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Designing and evaluating regional climate simulations for high latitude land use land cover change studies Tellus A (IF 1.932) Pub Date : 2020-12-03 P. A. Mooney; S. Sobolowski; H. Lee
Abstract High latitude regions are undergoing substantial land use and land cover change (LULCC) arising partly from a changing climate (e.g. greening of the Arctic) and climate mitigation policies (e.g. afforestation). Despite these ongoing changes, the impacts of LULCC in high latitudes are poorly understood. Studies to reduce this knowledge deficit primarily deploy regional climate models (RCMs)
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A dynamical–system description of precipitation over the tropics and the midlatitudes Tellus A (IF 1.932) Pub Date : 2020-11-23 Jun-Ichi Yano; Maarten H. P. Ambaum; Helen F. Dacre; Agostino Manzato
Abstract A dynamical–system approach is proposed to describe the relationship between precipitation and a chosen predictor. This is done by constructing a two dimensional phase space spanned by predictor and predictant. This study uses two sounding data sets from the Tropical Western Pacific and Friuli Venezia Giulia (FVG) over North–East Italy as representatives of the tropics and midlatitudes, in
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Dynamically weighted hybrid gain data assimilation: perfect model testing Tellus A (IF 1.932) Pub Date : 2020-11-13 Helena Barbieri De Azevedo; Luis Gustavo Gonçalves De Gonçalves; Eugenia Kalnay; Matthew Wespetal
Abstract Hybrid systems have become the state of the art among data assimilation methods. These systems combine the benefits of two other systems that are traditionally used in operational weather forecasting: an ensemble-based system and a variational system. One of the most recently proposed hybrid approaches is called hybrid gain (HG). It obtains the final analysis as a linear combination of two
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Accounting for observation uncertainty and bias due to unresolved scales with the Schmidt-Kalman filter Tellus A (IF 1.932) Pub Date : 2020-11-13 Zackary Bell; Sarah L. Dance; Joanne A. Waller
Abstract Data assimilation combines observations with numerical model data, to provide a best estimate of a real system. Errors due to unresolved scales arise when there is a spatio-temporal scale mismatch between the processes resolved by the observations and model. We present theory on error, uncertainty and bias due to unresolved scales for situations where observations contain information on smaller
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The impact of climate indices on precipitation variability in Baluchistan, Pakistan Tellus A (IF 1.932) Pub Date : 2020-11-13 Erum Aamir; Ishtiaq Hassan
Abstract Pakistan’s biggest province in terms of area, Baluchistan appears to have been affected from the climate variability since last few decades. No substantive research works have been carried out in analyzing the precipitation variability in Baluchistan and linkage to large-scale teleconnection. The goal of this paper is to determine possible linkages of precipitation with large scale atmospheric
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Measuring and restructuring the risk in forecasting drought classes: an application of weighted Markov chain based model for standardised precipitation evapotranspiration index (SPEI) at one-month time scale Tellus A (IF 1.932) Pub Date : 2020-11-10 Zulfiqar Ali; Ijaz Hussain; Amna Nazeer; Muhammad Faisal; Muhammad Ismail; Sadia Qamar; Marco Grzegorczyk; Faisal Maqbool Zahid; Guangheng Ni
Abstract Drought monitoring and forecasting play a vital role in making drought mitigation policies. In previous research, several drought monitoring tools based on the probabilistic models have been developed for precise and accurate inferences of drought severity and its effects. However, the risk of inaccurate determination of drought classes always exists in probabilistic models. The aim of this
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A novel spatially weighted accumulative procedure for regional drought monitoring Tellus A (IF 1.932) Pub Date : 2020-11-10 Rizwan Niaz; Ijaz Hussain; Zulfiqar Ali; Muhammad Faisal; Elsayed Elsherbini Elashkar; Alaa Mohamd Shoukry; Showkat Gani; Fares Fawzi Al-Deek
Abstract A variety of drought monitoring tools are being used for early warning systems and formulating drought mitigation policies. Standardized Drought Indices (SDI) are the most commonly used. However, the use of SDI at multiple stations located in a homogenous climatic region with internally similar characteristics and contagious in space arises several problems due to spatial and temporal behaviour
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Effect of quadric shear basic zonal flows and topography on baroclinic instability Tellus A (IF 1.932) Pub Date : 2020-11-09 Xiujie Zhang; Hongxin Zhang; Yuying Yang; Jian Song
Abstract On the β plane approximation, the two-layer quasigeostrophic mode is used to study the baroclinic instability of the quadric shear basic zonal flows on a uniform bottom topography. The phase speed and growth rate of instability waves are functions of the shear zonal basic flows and bottom topographic slope. The study focus is on the effects of topography and the quadric shear basic zonal flows
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Multi-year ocean thermal variability Tellus A (IF 1.932) Pub Date : 2020-10-24 Carl Wunsch
Abstract Numerous indicators show that multi-annual and longer oceanic baroclinic variability retains a complicated spatial structure out to decades and longer. With time-averaging, the sub-basin scales connected to abyssal topography and meteorological structures emerge in the fields. Here, using 26-years of an oceanic state estimate (ECCO), an attempt is made to extract simpler patterns from the
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Adding CO2 channel 16 to AHI data assimilation over land further improves short-range rainfall forecasts Tellus A (IF 1.932) Pub Date : 2020-10-30 Zhengkun Qin
Abstract The new generation of geostationary environmental operational satellite imager, the Himawari-8 Advanced Himawari Imager (AHI), adds two more water vapour channels and four more other channels than its predecessor, MTSAT-2. But except for the three water vapour channels, AHI channels are often not assimilated over land due to large uncertainty in surface parameters. Using the relative adjoint
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Evaluation of a sub-kilometre NWP system in an Arctic fjord-valley system in winter Tellus A (IF 1.932) Pub Date : 2020-10-28 Teresa Valkonen; Patrick Stoll; Yurii Batrak; Morten Køltzow; Thea Maria Schneider; Emmy E. Stigter; Ola B. Aashamar; Eivind Støylen; Marius O. Jonassen
Abstract Terrain challenges the prediction of near-surface atmospheric conditions, even in kilometre-scale numerical weather prediction (NWP) models. In this study, the ALADIN-HIRLAM NWP system with 0.5 km horizontal grid spacing and an increased number of vertical levels is compared to the 2.5-km model system similar to the currently operational NWP system at the Norwegian Meteorological Institute
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Development of the tangent linear and adjoint models of the MPAS-Atmosphere dynamic core and applications in adjoint relative sensitivity studies Tellus A (IF 1.932) Pub Date : 2020-09-16 Xiaoxu Tian; Xiaolei Zou
This study develops and tests a version of the Python-driven, non-hydrostatic Model for Prediction Across Scales – Atmosphere (MPAS-A) dynamic model, as well as its tangent linear and adjoint models. The non-linear, non-hydrostatic dynamic core of the MPAS-A is restructured to have a Python driver for the convenience of parsing namelists, manipulating matrices, controlling simulation time flows, reading
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Perturbation structure and evolution in tropical cyclones Noul and Nepartak based on singular vectors Tellus A (IF 1.932) Pub Date : 2020-09-04 John Chien-Han Tseng; Young-Sin Lai
This study examined tropical cyclones (TCs) Noul and Nepartak to demonstrate the evolutions of singular vector perturbations. Perturbations comprise eigen-solutions for dry total energy from two domains with different focuses, namely the TC itself and the background atmospheric flow in East Asia. These perturbations are usually used to construct ensemble members for the probabilistic forecasts of the
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Three-dimensional potential vorticity structures for extreme precipitation events on the convective scale Tellus A (IF 1.932) Pub Date : 2020-09-03 Annette Müller; Benjamin Niedrich; Peter Névir
Three-dimensional potential vorticity (PV) structures on the convective scale during extreme precipitation events are investigated. Using the high resolution COSMO-REA2 data set, 3D composites of the PV, with and without Coriolis parameter and related variables, are evaluated for different classes of precipitation intensity. The development of a significant horizontal dipole structure in the immediate
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Climate persistence and memory Tellus A (IF 1.932) Pub Date : 2020-08-18 Jiangnan Li; Zhian Sun
Abstract The autocorrelation function (ACF) and its relationship to fluctuation analysis (FA) are discussed, based on the reanalysis monthly mean geopotential height at 500 hPa from ECMWF (ERA-20C). ACF provides a measure of the influence of correlation at different time points. The principal pattern ACF shows relatively large positive correlations between every consecutive years in the central Asian
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On the contribution of internal climate variability to European future climate trends Tellus A (IF 1.932) Pub Date : 2020-07-31 T. Koenigk; L. Bärring; D. Matei; G. Nikulin; G. Strandberg; E. Tyrlis; S. Wang; R. Wilcke
Abstract Large historical and future ensemble simulations from the Max-Planck Institute and the Canadian Earth System Models and from CMIP5 have been analysed to investigate the uncertainty due to internal variability in multi-decadal temperature and precipitation trends over Europe. Internal variability dominates the uncertainties in temperature and precipitation trends in all seasons at 30-year time
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On the use of reduced grids in conjunction with the Equator-Pole grid system Tellus A (IF 1.932) Pub Date : 2020-07-15 Göran Starius
Abstract This is a continuation of a previous paper by Starius, where for the solution of the shallow water equations on the sphere, we consider Equator-Pole grid systems consisting of one latitude-longitude grid covering an annular band around the equator, and two orthogonal polar grids based on modified stereographic coordinates. Here, we generalise this by letting an equatorial band be covered with
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Regional drought assessment using improved precipitation records under auxiliary information Tellus A (IF 1.932) Pub Date : 2020-07-15 He Jiang; Muhammad Asif Khan; Zhilong Li; Zulfiqar Ali; Farman Ali; Sajid Gul
Abstract Changes in the climate and weather conditions, as well as rising earth’s average temperature are likely to escalate deterioration of global drought occurrence. Drought is considered an interwoven natural disaster composed by a number of different factors, as for example agricultural, meteorological or hydrological. Hydrological drought estimation with regional accuracy is the most problematic
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Occurrence and drivers of wintertime temperature extremes in Northern Europe during 1979–2016 Tellus A (IF 1.932) Pub Date : 2020-07-06 Cuijuan Sui; Lejiang Yu; Timo Vihma
Abstract Applying the daily ERA-interim reanalysis data from 1979 to 2016, we found that widespread cold (warm) wintertime extreme events in Northern Europe occurred most frequently in winter 1984–1985 (2006–2007). These events often persisted for multiple days, and their primary drivers were the pattern of atmospheric large-scale circulation, the direction of surface wind and the downward longwave
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An ensemble of perturbed analyses to approximate the analysis error covariance in 4dvar Tellus A (IF 1.932) Pub Date : 2020-06-05 H. Ngodock; I. Souopgui; M. Carrier; S. Smith; J. Osborne; J. D’Addezio
Abstract The analysis error covariance is not readily available from four-dimensional variational (4dvar) data assimilation methods, not because of the complexity of mathematical derivation, but rather its computational expense. A number of techniques have been explored for more readily obtaining the analysis error covariance such as using Monte–Carlo methods, an ensemble of analyses, or the adjoint
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Mediterranean overflow water in the North Atlantic and its multidecadal variability Tellus A (IF 1.932) Pub Date : 2020-06-04 Aitor Aldama-Campino; Kristofer DÖÖs
Abstract The Mediterranean overflow water is one of the most important intermediate-depth water masses in the North Atlantic. To investigate its properties a pre-industrial simulation with the earth system model EC-Earth is used. The multidecadal variability of the outflow is analysed by examining the modelled volume and salt transports through the Strait of Gibraltar as well as different atmospheric
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Towards assimilation of wind profile observations in the atmospheric boundary layer with a sub-kilometre-scale ensemble data assimilation system Tellus A (IF 1.932) Pub Date : 2020-05-19 Tobias Sebastian Finn; Gernot Geppert; Felix Ament
Abstract Wind profile observations near the surface are rarely assimilated into numerical weather prediction models. More and more ground-based remote sensing devices for wind profile observations are used to get profiles up to the hub height of wind turbines. However, an observation impact of LiDAR-like wind profile measurements on data assimilation in the atmospheric boundary layer is unknown. We
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Multi-nested WRF simulations for studying planetary boundary layer processes on the turbulence-permitting scale in a realistic mesoscale environment Tellus A (IF 1.932) Pub Date : 2020-05-14 Hans-Stefan Bauer; Shravan Kumar Muppa; Volker Wulfmeyer; Andreas Behrendt; Kirsten Warrach-Sagi; Florian Späth
Abstract The Weather Research and Forecasting (WRF) model was applied in a nested configuration from a 2.7 km convection-permitting domain via grey-zone resolutions of 900 m and 300 m down to the 100 m turbulence-permitting scale. Based on sensitivity studies, this approach was optimized to investigate the evolution of small-scale processes in the PBL for a clear sky case during the HOPE experiment
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Identifying remote sources of interannual variability for summer precipitation over Nordic European countries tied to global teleconnection wave patterns Tellus A (IF 1.932) Pub Date : 2020-05-12 Ramón Fuentes-Franco; Torben Koenigk
Abstract We show evidence that tropical atmospheric variability over the central tropical Pacific modulates the circulation over the western Arctic and the North Atlantic-European sector, impacting the summer precipitation especially over Nordic European countries (NEC). Our results, based on the ERA5 reanalysis, suggest the occurrence of a teleconnection mechanism (similar to the Pacific North American
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The extratropical transition of Hurricane Ophelia (2017) as diagnosed with a generalized omega equation and vorticity equation Tellus A (IF 1.932) Pub Date : 2020-02-03 Mika Rantanen; Jouni Räisänen; Victoria A. Sinclair; Juha Lento; Heikki Järvinen
Abstract Hurricane Ophelia was a category 3 hurricane which underwent extratropical transition and made landfall in Europe as an exceptionally strong post-tropical cyclone in October 2017. In Ireland, Ophelia was the worst storm in 50 years and resulted in significant damage and even loss of life. In this study, the different physical processes affecting Ophelia’s transformation from a hurricane to
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A novel generalized combinative procedure for Multi-Scalar standardized drought Indices-The long average weighted joint aggregative criterion Tellus A (IF 1.932) Pub Date : 2020-03-11 Zulfiqar Ali; Ibrahim M. Almanjahie; Ijaz Hussain; Muhammad Ismail; Muhammad Faisal
Abstract Drought hazards have complex climatic and spatio-temporal features. Therefore, its accurate monitoring is a challenging task in hydrological research. In recent, the use of standardized drought indices for drought monitoring is common in practice. However, the existence of several drought indices creates chaotic problems in data mining and decision making. This article presents a new weighting
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Using land-based stations for air–sea interaction studies Tellus A (IF 1.932) Pub Date : 2019-12-09 Anna Rutgersson; Heidi Pettersson; Erik Nilsson; Hans Bergström; Marcus B. Wallin; E. Douglas Nilsson; Erik Sahlée; Lichuan Wu; E. Monica Mårtensson
Abstract In situ measurements representing the marine atmosphere and air–sea interaction are taken at ships, buoys, stationary moorings and land-based towers, where each observation platform has structural restrictions. Air–sea fluxes are often small, and due to the limitations of the sensors, several corrections are applied. Land-based towers are convenient for long-term observations, but one critical
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Changes in daily and cumulative volumetric rainfall at various intensity levels due to urban surface expansion over China Tellus A (IF 1.932) Pub Date : 2020-03-30 Deming Zhao; Jinlin Zha; Jian Wu
Abstract Urban surface expansion affects land–atmosphere interactions as well as rainfall. Both the subregional area-averaged daily (DRAIN) and the subregional cumulative volumetric (VRAIN) rainfall amounts are important in this context for hydrological applications and management. Conducted at the city (Beijing, Shanghai, and Guangzhou), city cluster (Beijing–Tianjin–Hebei (BTH), the Yangtze River
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A potential application of height-dependent cloud emission and scattering indices for identifying CrIS clear channels above clouds Tellus A (IF 1.932) Pub Date : 2019-11-29 Z. Niu; X. Zou
Abstract Satellite data assimilation of hyperspectral Cross-track Infrared Sounder (CrIS) clear channels in regions with but not affected by low-level clouds requires a set of height-dependent cloud emission and scattering indices (CESIs) that are sensitive to cloud top pressures. In this study, three CESIs are generated by pairing CrIS longwave and shortwave channels at three altitudes around 212
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Global variability in radiative-convective equilibrium with a slab ocean under a wide range of CO2 concentrations Tellus A (IF 1.932) Pub Date : 2020-01-07 Gabor Drotos; Tobias Becker; Thorsten Mauritsen; Bjorn Stevens
Abstract In radiative-convective equilibrium (RCE), radiative cooling of the troposphere is roughly balanced by the vaporization enthalpy set free by precipitating moist convection. Many earlier studies restricted the investigation of RCE to the dynamics of the atmosphere with constant boundary conditions including prescribed surface temperature. We investigate a GCM setup where a slab ocean is coupled
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Improving the condition number of estimated covariance matrices Tellus A (IF 1.932) Pub Date : 2019-12-13 Jemima M. Tabeart; Sarah L. Dance; Amos S. Lawless; Nancy K. Nichols; Joanne A. Waller
Abstract High dimensional error covariance matrices and their inverses are used to weight the contribution of observation and background information in data assimilation procedures. As observation error covariance matrices are often obtained by sampling methods, estimates are often degenerate or ill-conditioned, making it impossible to invert an observation error covariance matrix without the use of
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Probabilistic thunderstorm forecasting by blending multiple ensembles Tellus A (IF 1.932) Pub Date : 2020-01-07 François Bouttier; Hugo Marchal
Abstract In numerical weather prediction models, point thunderstorm forecasts tend to have little predictive value beyond a few hours. Thunderstorms are difficult to predict due largely to their typically small size and correspondingly limited intrinsic predictability. We present an algorithm that predicts the probability of thunderstorm occurrence by blending multiple ensemble predictions. It combines
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Impact of climate change on the climatology of Vb cyclones Tellus A (IF 1.932) Pub Date : 2020-02-11 Martina Messmer; Christoph C. Raible; Juan José Gómez-Navarro
Abstract Extratropical cyclones of type Vb develop over the western Mediterranean and move north-eastward, leading to heavy precipitation over central Europe and posing a major natural hazard. Thus, this study aims at assessing their sensitivity to climate change and deepens the understanding of the underlying processes of Vb-type cyclones. The analysis is based on global climate model output, which
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Analyses of the relationship between drought occurrences and their causal factors in Tigray Region, Northern Ethiopia Tellus A (IF 1.932) Pub Date : 2020-01-29 A.S. Tefera; J.O. Ayoade; N.J. Bello
Abstract Drought is controlled and enhanced by changes in the local and global climate factors. The changes in the global factors mainly occur on the vast oceanic surfaces, while the changes in the local factors occur in the area of drought influence. In order to skilfully forecast and monitor drought occurrences, it is crucial that the specific causal factors be identified and their links studied
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Improving the representation of supercooled liquid water in the HARMONIE-AROME weather forecast model Tellus A (IF 1.932) Pub Date : 2019-12-17 Bjørg Jenny Kokkvoll Engdahl; Gregory Thompson; Lisa Bengtsson
Abstract A realistic representation of mixed-phase clouds in weather and climate models is essential to accurately simulate the model’s radiative balance and water cycle. In addition, it is important for providing downstream applications with physically realistic model data for computation of, for instance, atmospheric icing on societal infrastructure and aircraft. An important quantity for forecasts
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A numerical integration-based Kalman filter for moderately nonlinear systems Tellus A (IF 1.932) Pub Date : 2020-01-27 Sarah A. King; Kazufumi Ito; Daniel Hodyss
Abstract This paper introduces a computationally efficient data assimilation scheme based on Gaussian quadrature filtering that potentially outperforms current methods in data assimilation for moderately nonlinear systems. Moderately nonlinear systems, in this case, are systems with numerical models with small fourth and higher derivative terms. Gaussian quadrature filters are a family of filters that
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Nonlinear interaction of gravity and acoustic waves Tellus A (IF 1.932) Pub Date : 2020-01-10 André Seiji Wakate Teruya; Carlos Frederico Mendonça Raupp
Abstract Here we have investigated the possibility of an inertio-acoustic wave-mode to be unstable with regards to gravity mode perturbations through non-linear triad interactions in the context of a shallow non-hydrostatic model. We have considered highly truncated Galerkin expansions of the perturbations around a resting, hydrostatic and isothermal background state in terms of the eigensolutions
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Evaluations of Uncertainty and Sensitivity in Soil Moisture Modeling on the Tibetan Plateau Tellus A (IF 1.932) Pub Date : 2019-12-20 Fei Peng; Mu Mu; Guodong Sun
Abstract To provide scientific support for improvements in land surface modeling on the Tibetan Plateau (TP) by reducing uncertainties in the physical parameters of models, comprehensive uncertainty and sensitivity evaluations were performed for the simulation of surface soil moisture (SSM). Five observational stations were selected for the study. The conditional nonlinear optimal perturbation related
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Temperature and precipitation during winter in NyÅlesund, Svalbard and possible tropical linkages Tellus A (IF 1.932) Pub Date : 2020-04-11 M. Nuncio; Sourav Chatterjee; K. Satheesan; Sheeba Nettukandy Chenoli; Subeesh M.P.
Abstract Winter (DJF) temperature and precipitation variability in an Arctic Archipelago, Svalbard is investigated for an extreme event during December 2015 as well as on interannual time scales. During December 2015–16, a strong high pressure anomaly over northern Europe channelised warm and moist air into Ny Ålesund (∼79°N and ∼11°E) resulting in extreme temperature and precipitation. This high pressure
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Assimilation of semi-qualitative sea ice thickness data with the EnKF-SQ: a twin experiment Tellus A (IF 1.932) Pub Date : 2019-12-14 Abhishek Shah; Laurent Bertino; François Counillon; Mohamad El Gharamti; Jiping Xie
Abstract A newly introduced stochastic data assimilation method, the Ensemble Kalman Filter Semi-Qualitative (EnKF-SQ) is applied to a realistic coupled ice-ocean model of the Arctic, the TOPAZ4 configuration, in a twin experiment framework. The method is shown to add value to range-limited thin ice thickness measurements, as obtained from passive microwave remote sensing, with respect to more trivial
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Changes in the hydrodynamic characteristics of the upper layer of the South China Sea during the period of super typhoon Rammasun (2014) Tellus A (IF 1.932) Pub Date : 2020-03-02 Dongyang Fu; Xiaolong Zhang; Xue Li; Dazhao Liu; Guo Yu; Huabing Xu
Abstract Severe typhoon Rammasun (2014) was strengthened (super typhoon) in the east of the Leizhou Peninsula before moving into the Beibu Gulf. This study used the empirical orthogonal function (EOF) method to analyze the spatiotemporal variations in the sea surface wind (SSW), surface level anomaly (SLA), sea surface temperature (SST), mixed layer depth (MLD) and precipitation of the SCS. The study
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Observational evidence that a feedback control system with proportional-integral-derivative characteristics is operating on atmospheric surface temperature at global scale Tellus A (IF 1.932) Pub Date : 2020-02-24 L. Mark W. Leggett; David A. Ball
Abstract Here we provide statistically significant observational evidence that a feedback control system moderating atmospheric temperature is presently operating coherently at global scale. Further, this control system is of a sophisticated type, involving the corrective feedback not only of a linear error term but also its derivative and its integral. This makes it of the same type as the most widely
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A simple theory for the modulation of tropical instability waves by ENSO and the annual cycle Tellus A (IF 1.932) Pub Date : 2019-12-17 Julien Boucharel; Fei-Fei Jin
Abstract Motivated by a recent active period of Tropical Instability Waves (TIWs) that followed the extreme 2015/2016 El Niño, we developed a stochastically forced linear model for TIWs with its damping rate modulated by the annual cycle and El Niño Southern Oscillation (ENSO). The model’s analytical and numerical solutions capture relatively well the observed Pacific TIWs amplitude variability dominated
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Climate models disagree on the sign of total radiative feedback in the Arctic Tellus A (IF 1.932) Pub Date : 2019-12-04 Karoline Block; Florian A. Schneider; Johannes Mülmenstädt; Marc Salzmann; Johannes Quaas
Abstract Climate feedbacks have been found to strongly impact the observed amplified Arctic warming. However, Arctic amplification is modeled with a wide spread which partly arises from intermodel differences of the various feedbacks. To explain the spread in modeled Arctic warming, feedback uncertainties and their origins are investigated in 13 climate models in an experiment with abruptly quadrupled
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Impact of the variational assimilation of ground-based GNSS zenith total delay into AROME-Morocco model Tellus A (IF 1.932) Pub Date : 2020-01-03 Fatima Zahra Hdidou; Soumia Mordane; Patrick Moll; Jean-François Mahfouf; Hassnae Erraji; Zaineb Dahmane
Abstract The impact of assimilating zenith total delay (ZTD) observations from the Moroccan ground-based Global Navigation Satellite System (GNSS) network into the high-resolution operational model AROME-Morocco (2.5 km) is assessed over one month. The objective is to investigate the impact on moisture field and rainy event forecasts in a three-dimensional variational (3D-Var) data assimilation framework
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Predictive verification for the design of partially exchangeable multi-model ensembles Tellus A (IF 1.932) Pub Date : 2019-12-18 Zied Ben Bouallégue; Christopher A. T. Ferro; Martin Leutbecher; David S. Richardson
Abstract The performance of an ensemble forecast, as measured by scoring rules, depends on its number of members. Under the assumption of ensemble member exchangeability, ensemble-adjusted scores provide unbiased estimates of the ensemble-size effect. In this study, the concept of ensemble-adjusted scores is revisited and exploited in the general context of multi-model ensemble forecasting. In particular
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A balanced state consistent with planetary-scale motion for quasi-geostrophic dynamics Tellus A (IF 1.932) Pub Date : 2019-12-04 Woosok Moon; James y-k. Cho
Abstract The role of planetary-scale zonally-asymmetric thermal forcing on large-scale atmospheric dynamics is crucial for understanding low-frequency phenomena in the atmosphere. Despite its paramount importance, good theoretical foundation for the understanding is still lacking. Here, we address this issue by providing a general framework for including planetary-scale thermal forcing in large-scale
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Application of observability Gramian to targeted observation in WRF data assimilation Tellus A (IF 1.932) Pub Date : 2019-12-06 Ryoichi Yoshimura; Aiko Yakeno; Takashi Misaka; Shigeru Obayashi
Abstract The optimal observation placement in weather forecast and research (WRF) data assimilation is investigated using a sensitivity analysis method. The method quantifies the sensitivity of observation location to assimilated results as an unobservability index. The empirical observability Gramian matrix composed from a time series of WRF model outputs is used to obtain the unobservability index
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Impact of strong and extreme El Niños on European hydroclimate Tellus A (IF 1.932) Pub Date : 2020-01-07 Martin P. King; Entao Yu; Jana Sillmann
Abstract The question of European hydroclimate anomaly associated with El Niño-Southern Oscillation (ENSO) is revisited by composite analyses on data from Dai et al.’s Palmer Drought Severity Index, the Old World Drought Atlas (OWDA), and a 10-member CESM coupled-model Last Millennium Ensemble (CESM-LME) simulations. This study benefits from exceptionally long or large samples in OWDA and CESM-LME
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