Journal of Earth System Science ( IF 1.3 ) Pub Date : 2020-10-20 , DOI: 10.1007/s12040-020-01487-w P V S Raju , Akhilesh Mishra , A B T Sundari
Abstract
The diagnosis of the summer monsoon features over India are investigated using global analysis and forecast system (GFS) of the National Center for Environmental Prediction (NCEP). In addition, the performance of the NCEP GFS model in capturing the observed rainfall variability of the summer monsoon features over India through diagnostic parameters. We delineate the variability between two normal monsoon seasons with basic meteorological fields and significant parameters of kinetic energy, heat and moisture budgets. The 1200 UTC operational analyses and forecasts (day1 through day5) data for summer monsoon seasons of June, July, August and September (JJAS) of 2010 and 2011 are considered. Although both are normal monsoon seasons with seasonal rainfall (JJAS) departure of about −3.1% and 2.1% respectively, during 2010 and 2011, some differences are observed in the spatial distribution of rainfall. The diagnostic fields reasonably reproduced the variations in analyses and forecast fields of up to 5 days. The model forecasts of day1 delineated that the Indian summer monsoon features are well captured, whereas in day3 and day5, forecast depicts some differences. Overall the NCEP analysis and forecast fields not only produces mean monsoonal flow, but also captures seasonal variability realistically. This is evident from the large-scale balances represented by the analyses and model forecasts.
Highlights
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The NCEP global analyses and forecast System depicts less bias in low level circulation in day1 with respect to analysis field, albeit, this bias is increases with increase of forecast period. Overall, the mean monsoon circulation is captured by the NCEP analyzes and forecast system fairly well.
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The forecast fields illustrate the warm bias in the low levels with maximum over northwest India and monsoon through region, These warm bias in the forecast fields is due to the higher specific humidity over the monsoon trough region.
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In the forecast of day1, day3 and day5 show the warm bias in the low levels at 925 hPa with maximum over northwest India and monsoon trough region, whereas cold bias is observed over Gujarat and Western Ghat in day3 and day5 forecast.
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The significant seasonal variability perceived in two normal summer monsoon rainfall. This variability is captured by analysis and model forecasts realistically in terms of diagnostic fields of kinetic energy, heat and moisture.
中文翻译：
NCEP分析和预报系统中的印度夏季风特征
摘要
使用国家环境预测中心（NCEP）的全球分析和预报系统（GFS）对印度夏季风特征进行诊断。此外，NCEP GFS模型通过诊断参数捕获印度整个夏季季风特征观测到的降雨变化的性能。我们用基本的气象学领域和动能，热量和水分预算的重要参数描述了两个正常的季风季节之间的变化。考虑了2010年和2011年6月，7月，8月和9月（JJAS）的夏季季风季节的1200 UTC运行分析和预测（第1天到第5天）数据。尽管两个季节均为正常的季风季节，但季节性降雨（JJAS）的离去分别约为-3.1％和2.1％，但在2010年和2011年，降雨的空间分布存在一些差异。诊断字段合理地再现了长达5天的分析和预测字段中的变化。第1天的模型预测表明，印度夏季风特征被很好地捕获，而在第3天和第5天，预测描绘出一些差异。总体而言，NCEP分析和预报领域不仅产生了季风平均流量，而且还实际地捕获了季节变化。从分析和模型预测所代表的大规模余额中可以明显看出这一点。预测描述了一些差异。总体而言，NCEP分析和预报领域不仅产生了季风平均流量，而且还实际地捕获了季节变化。从分析和模型预测所代表的大规模余额中可以明显看出这一点。预测描述了一些差异。总体而言，NCEP分析和预报领域不仅产生了季风平均流量，而且还实际地捕获了季节变化。从分析和模型预测所代表的大规模余额中可以明显看出这一点。
强调
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NCEP全球分析和预报系统显示，第一天低水平环流相对于分析领域的偏差较小，尽管这种偏差随着预报期的增加而增加。总体而言，NCEP分析和预报系统可以很好地捕获平均季风环流。
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预报场显示了印度西北部和整个季风地区的低水平暖偏，最高值。这些预报场中的暖偏是由于季风槽区比湿较高。
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在第1天的预测中，第3天和第5天在925 hPa处显示低水平的暖偏差，在印度西北部和季风槽区最大，而在第3天和第5天的预报中在古吉拉特邦和西高止山脉观测到冷偏差。
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在两个正常的夏季季风降雨中，季节变化显着。根据动能，热量和水分的诊断范围，可以通过分析和模型预测来实际捕获这种可变性。
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