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Tropical precipitation simulated by the NCAR Community Climate Model (CCM3): An evaluation based on TRMM satellite measurements.

机译：NCAR社区气候模型（CCM3）模拟的热带降水：基于TRMM卫星测量的评估。

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摘要

This study evaluates the simulation of tropical precipitation by the Community Climate Model, Version 3, developed at the National Center for Atmospheric Research. For an evaluation of the annual cycle of precipitation, monthly-mean precipitation rates from an ensemble of CCM3 simulations are compared to those computed from observations of the TRMM satellite over a 44-month period. On regional and sub-regional scales, the comparison fares well over much of the Eastern Hemisphere south of 10°S and over South America. However, model-satellite differences are large in portions of Central America and the Caribbean, the southern tropical Atlantic, the northern Indian Ocean, and the western equatorial and southern tropical Pacific. Since precipitation in the Tropics is the primary source of latent energy to the general circulation, such large model-satellite differences imply large differences in the amount of latent energy released. Differences are seasonally-dependent north of 10°N, where model wet biases occur in realistic wet seasons or model-generated artificial wet seasons. South of 10°N, the model wet biases exist throughout the year or have no recognizable pattern.; For an evaluation of the diurnal cycle of precipitation, hourly-averaged precipitation rates from the same ensemble of simulations and for the same 44-month period are compared to observations from the Tropical Rainfall Measuring Mission (TRMM) satellite. Comparisons are made for 15° longitude x 10° latitude boxes and for larger geographical areas within the Tropics. The temporally- and spatially-averaged hourly precipitation rates from CCM3 and from TRMM are fit to the diurnal harmonic by the method of linear least-squares regression, and the phases and the amplitudes of the diurnal cycles are compared. The model's diurnal cycle is too strong over major land masses, particularly over South America (by a factor of 3), and is too weak over many oceans, particularly the northwestern Tropical Pacific (by a factor of 2). The model-satellite phase differences tend to be more homogeneous. The peak in the daily precipitation in the model consistently precedes the observations nearly everywhere. Phase differences are large over Australia, Papua New Guinea, and Saharan Africa, where CCM3 leads TRMM by 4 hours, 5 to 6 hours, and 9 to 11 hours respectively. A model sensitivity experiment shows that increasing the convective adjustment time scale in the model's deep convective parameterization reduces its positive amplitude bias over land regions but has no effect on the phase of the diurnal cycle.
机译：这项研究通过在国家大气研究中心开发的社区气候模型第3版评估了热带降水的模拟。为了评估年降水周期，将来自CCM3模拟集合的月平均降水率与根据TRMM卫星在44个月的观测中得出的值进行了比较。在区域和次区域范围内，该比较在南半球10°S以南的大部分东半球和南美均具有良好的优势。但是，中美洲和加勒比海地区，南部热带大西洋，北部印度洋以及赤道西部和热带南部太平洋地区的卫星模型差异很大。由于热带地区的降水是整个环流潜在能量的主要来源，因此，这种巨大的卫星模型差异意味着所释放的潜在能量差异很大。差异是在10°N以北随季节变化的，在实际的湿润季节或模型产生的人工湿润季节中，会出现模型湿偏。在10°N以南，模型的湿偏差全年存在或没有可识别的模式。为了评估降水的昼夜周期，将来自相同模拟组和相同44个月期间的每小时平均降水率与来自热带雨量测量团（TRMM）卫星的观测值进行了比较。对15°经度x 10°纬度框和热带地区较大的地理区域进行了比较。利用线性最小二乘回归方法，将CCM3和TRMM的时空平均小时降水率拟合到昼夜谐波，并比较了昼夜周期的相位和幅度。在主要陆地上，该模型的日周期过强，特别是在南美（3倍），而在许多海洋上，尤其是西北热带太平洋，则太弱（每天2倍）。卫星模型的相位差往往更均匀。该模型中每天降水的峰值几乎始终在观测之前。在澳大利亚，巴布亚新几内亚和撒哈拉以南非洲，相差很大，在这些国家，CCM3领先TRMM分别为4小时，5至6小时和9至11小时。模型敏感性实验表明，在模型的深层对流参数化过程中增加对流调整时间尺度会降低其在陆地区域上的正振幅偏差，但对昼夜周期的相位没有影响。

著录项

  • 作者

    Collier, Jonathan Craig.;

  • 作者单位

    Texas A&M University.;

  • 授予单位 Texas A&M University.;
  • 学科 Physics Atmospheric Science.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 129 p.
  • 总页数 129
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 大气科学（气象学）;
  • 关键词

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