During the 1990 SARMAP/AUSPEX study a network of rawinsondes was flown at 3- and 6-h intervals to evaluate the meteorological conditions conducive high ozone concentrations in the Central Valley of California. Vertical profiles of air temperature, humidity, and pressure from 9 of the sites were used to determine maximum daily mixing heights in California’s San Joaquin Valley (SJV) during the period August 3–6, 1990 and to evaluate their spatial distribution. The analysis showed a general pattern of increasing mixing heights from north to south within the SJV. But, it also showed that mixing heights were lower in areas in proximity to irrigated agriculture. The WRF prognostic meteorological model was used to simulate mixing heights during this period using three land surface modules (LSM): thermal diffusion (TD), Noah, and Pleim-Xiu (PXU). The maximum daily mixing heights simulated using the TD LSM were generally negatively biased; while those simulated using the Noah and PXU LSMs were positively biased. The differences in simulated mixing heights were attributed to differences in how crop land irrigation water is represented within each LSM. The TD LSM effectively assumes a fixed soil water content, but of sufficient magnitude to reflect latent heat fluxes associated with crop land irrigation. The PXU and Noah LSMs include comprehensive descriptions of the soil water budget. However, soil water may be depleted in the arid summer climate and these LSMs provide no direct means of accounting for water added through irrigation. The LSMs were also sensitive to estimates of ground cover in irrigated areas. For all 9 sites, the root mean square error (RMSE) for maximum daily mixing heights for the TD LSM, the Noah LSM, and the PXU LSM was 269, 350, and 366 m, respectively; and the biases for the 9 sites were − 161, 355, and 437 m, respectively. Using the assumption of well-managed irrigation and leaf area index (LAI) estimates from AVHRR remote sensing data sets, adjustments to the WRF input files were made to update soil water contents and ground cover for irrigated crop land use. Using the Noah LSM with the adjusted files, site-specific mixing height biases were reduced up to a factor of 4 and, for all sites, the RMSE for maximum daily mixing heights were reduced from 350 to 260 m; for the PXU LSM RMSEs were reduced from 366 to 238 m; and for the TD LSM from 269 to 231 m. This analysis illustrates the importance of accounting for the effects of applied irrigation water and ground cover in the simulation of mixing heights during the arid summer within the SJV. Irrigation can influence actual mixing heights and their distribution within a domain. It also illustrates that the choice of LSM is of less importance than setting LSM parametrizations to values appropriate for the modeling domain.

在1990年的SARMAP / AUSPEX研究中，以3小时和6小时的间隔飞行了一个拉丁森德网络，以评估导致加利福尼亚中央山谷高臭氧浓度的气象条件。使用1990年8月3日至6日期间加利福尼亚州圣华金河谷（SJV）的9个站点的垂直温度，湿度和压力的垂直剖面来确定最大每日混合高度，并评估它们的空间分布。分析表明，在SJV中，混合高度从北向南逐渐增加。但是，这也表明在灌溉农业附近的地区混合高度较低。在此期间，使用WRF预后气象模型模拟了三个地面模块（LSM）的混合高度：热扩散（TD），Noah和Pleim-Xiu（PXU）。使用TD LSM模拟的最大每日混合高度通常会产生负偏差。而使用Noah和PXU LSM进行模拟的那些则有正偏见。模拟混合高度的差异归因于每个LSM中农田灌溉水的表示方式差异。TD LSM有效地假定土壤含水量固定，但大小足以反映与农田灌溉相关的潜热通量。PXU和Noah LSM包括对土壤水预算的全面描述。但是，在干旱的夏季气候中，土壤水可能会枯竭，而这些LSM并不能直接说明通过灌溉增加的水量。LSM对灌溉区域的地面覆盖率估算也很敏感。对于所有9个网站，TD LSM，Noah LSM和PXU LSM的最大每日混合高度的均方根误差（RMSE）分别为269、350和366 m；9个位置的偏向分别为-161、355和437 m。使用来自AVHRR遥感数据集的良好管理的灌溉和叶面积指数（LAI）估计值的假设，对WRF输入文件进行了调整，以更新土壤水含量和灌溉农田的地表覆盖率。使用带有调整过的文件的Noah LSM，可以将特定地点的混合高度偏差降低至4倍，并且对于所有地点，最大每日混合高度的RMSE将从350降低至260 m；PXU LSM的RMSE从366减少到238 m；而TD LSM则为269至231 m。该分析说明了在SJV干旱夏季模拟混合高度时，考虑灌溉水和地面覆盖物影响的重要性。灌溉会影响实际的混合高度及其在域内的分布。它还说明，与将LSM参数设置为适合建模域的值相比，选择LSM的重要性较小。