Jasinski Michael F, Borak Jordan S, Kumar Sujay V, Mocko David M, Peters-Lidard Christa D, Rodell Matthew, Rui Hualan, Beaudoing Hiroko K, Vollmer Bruce E, Arsenault Kristi R, Li Bailing, Bolten John D, Tangdamrongsub Natthachet
Hydrological Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland.
Earth System Science Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland.
J Hydrometeorol. 2019 Aug;20(8):1595-1617. doi: 10.1175/jhm-d-17-0234.1. Epub 2019 Jul 30.
Terrestrial hydrologic trends over the conterminous United States are estimated for 1980-2015 using the National Climate Assessment Land Data Assimilation System (NCA-LDAS) reanalysis. NCA-LDAS employs the uncoupled Noah version 3.3 land surface model at 0.125°× 1258° forced with NLDAS-2 meteorology, rescaled Climate Prediction Center precipitation, and assimilated satellite-based soil moisture, snow depth, and irrigation products. Mean annual trends are reported using the nonparametric Mann-Kendall test at < 0.1 significance. Results illustrate the interrelationship between regional gradients in forcing trends and trends in other land energy and water stores and fluxes. Mean precipitation trends range from +3 to +9 mm yr in the upper Great Plains and Northeast to -1 to -9 mm yr in the West and South, net radiation flux trends range from 10.05 to 10.20 W m yr in the East to -0.05 to -0.20 W m yr in the West, and U.S.-wide temperature trends average about +0.03 K yr. Trends in soil moisture, snow cover, latent and sensible heat fluxes, and runoff are consistent with forcings, contributing to increasing evaporative fraction trends from west to east. Evaluation of NCA-LDAS trends compared to independent data indicates mixed results. The RMSE of U.S.-wide trends in number of snow cover days improved from 3.13 to 2.89 days yr while trend detection increased 11%. Trends in latent heat flux were hardly affected, with RMSE decreasing only from 0.17 to 0.16 W m yr, while trend detection increased 2%. NCA-LDAS runoff trends degraded significantly from 2.6 to 16.1 mm yr while trend detection was unaffected. Analysis also indicated that NCA-LDAS exhibits relatively more skill in low precipitation station density areas, suggesting there are limits to the effectiveness of satellite data assimilation in densely gauged regions. Overall, NCA-LDAS demonstrates capability for quantifying physically consistent, U.S. hydrologic climate trends over the satellite era.
利用国家气候评估陆地数据同化系统（NCA-LDAS）再分析数据，估算了1980 - 2015年美国本土的陆地水文趋势。NCA-LDAS采用非耦合的诺亚3.3版陆面模型，分辨率为0.125°×0.125°，由NLDAS-2气象数据、重新缩放的气候预测中心降水数据以及同化的基于卫星的土壤湿度、积雪深度和灌溉产品驱动。使用非参数曼-肯德尔检验报告年平均趋势，显著性水平<0.1。结果说明了强迫趋势的区域梯度与其他陆地能量、水储量和通量趋势之间的相互关系。年平均降水趋势范围从大平原上游和东北部的+3至+9毫米/年到西部和南部的-1至-9毫米/年，净辐射通量趋势范围从东部的10.05至10.20瓦/平方米/年到西部的-0.05至-0.20瓦/平方米/年，全美国范围的温度趋势平均约为+0.03开尔文/年。土壤湿度、积雪覆盖、潜热通量和感热通量以及径流的趋势与强迫因素一致，导致蒸发分数趋势从西向东增加。将NCA-LDAS趋势与独立数据进行比较的评估结果喜忧参半。全美国范围积雪天数趋势的均方根误差从3.13天/年改善到2.89天/年，而趋势检测增加了11%。潜热通量趋势几乎没有受到影响，均方根误差仅从0.17瓦/平方米/年降至0.16瓦/平方米/年，而趋势检测增加了2%。NCA-LDAS径流趋势从2.6毫米/年显著恶化至16.1毫米/年，而趋势检测未受影响。分析还表明，NCA-LDAS在低降水站点密度地区表现出相对更高的技能，这表明在密集测量区域，卫星数据同化的有效性存在局限性。总体而言，NCA-LDAS展示了在卫星时代量化美国物理上一致的水文气候趋势的能力。
