Influence of Anamalous Eurasian Spring Snow Cover on the Indian Summer Monsoon

有强有力的经验证据表明，欧亚春季积雪的面积与随后印度上空夏季降雨量呈负相关。本研究的目的是通过大气环流模式(GCM)的一系列实验来研究这一经验关系的有效性。GCM是一个全球谱模式，在波数为40的水平分辨率下进行菱形截断，垂直方向上有18层。物理过程包括：地表生物物理过程、日循环、浅层和深层对流、云-辐射相互作用以及大尺度和亚网格尺度地形的影响。为了研究春季欧亚积雪对夏季风环流的影响，提出了三个不同面积和深度的欧亚积雪覆盖实验。这三个实验都将模拟从3月1日到9月30日的年度循环模式的全球整体环流。这些模拟的差异只是因为3月1日欧亚大陆的规定降雪范围和深度。所有其他规定的量将来自气候学。第一个实验是通过规定一个与1970年春季观测到的最小降雪量相似的最小降雪量，来确定降雪量负异常对季风环流的影响。在本实验中，PI将使用平均积雪深度。第二个和第三个实验旨在调查与1972年春季观测到的降雪范围类似的正异常的影响。在第二个实验中，PI规定了最小积雪深度，以隔离表面反照率的影响。在第三个实验中，他将规定最大降雪量，以研究反照率的影响以及融化和蒸发的影响。这些异常实验的结果将与控制模拟进行比较，以检验这些结果的统计意义。这项研究之所以重要，是因为它试图改善我们对气候系统的重要组成部分、地面边界强迫和季风之间的关系的理解。

There is strong empirical evidence that the areal extent of Eurasian spring snow cover is negatively correlated with the following summer rainfall over rainfall over India. The purpose of this research is to study the validity of this empirical relationship from a series of experiments with a general circulation model (GCM). The GCM is a global spectral model with rhomboidal truncation at wave number 40 horizontal resolution with 18 layers in the vertical. The physical processes include: surface biophysical processes, diurnal cycle, shallow and deep convection, cloud-radiation interaction and effects of large-scale and subgrid- scale orography. Three experiments are proposed with varying areal extent and depth of the Eurasian snow cover in the spring to study its influence on the summer monsoon circulations. All three experiments will simulate ensemble global circulations in an annual cycle mode from March 1 though September 30. The difference in these simulations are only due to the prescribed snow extent and depth over Eurasia on March 1. All other prescribed quantities will come from climatology. The first experiment is to determine the impact of a negative anomaly in the snow extent on the monsoon circulations by prescribing a minimum snow extent similar to that observed during the spring of 1970. In this experiment the PI will use average snow depth. The second and third experiments are designed to investigate the impact of a positive anomaly in the snow extent similar to that observed during the spring of 1972. In the second experiment the PI prescribe a minimum snow depth in order to isolate the effects of the surface albedo. In the third experiment he will prescribe a maximum snow in order to study the effects of albedo as well as the effects of melting and evaporation. The results of these anomaly experiments will be compared with the control simulations to test the statistical significance of these results..This research is important because it seeks to improve our understanding of relationships between important components of the climate system, surface boundary forcing and monsoons.