Journal of Tropical Oceanography >
A quality control method based on gradient information of microwave radiation data AMSU-A
Received date: 2016-05-10
Request revised date: 2016-12-13
Online published: 2017-04-06
Supported by
Public Science and Technology Research Funds Projects of Meteorology (GYHY201506002, GYHY201506022)
National Natural Science Foundation of China (41375106)
Copyright
Quality control (QC) is a key for microwave sounding radiance data assimilation in numerical weather prediction (NWP) models. In this study, a new approach of QC for Advanced Microwave Sounding Unit-A (AMSU-A) radiance was developed by introducing brightness temperature gradient of view point. In this approach, the data were considered to be contaminated by precipitation if their gradients were anomalously large, and would be discarded. Two typhoon cases, Kalmaegi in 2008 and Kompasu in 2010, were simulated by WRF (Weather Research and Forecasting) model to see the impacts of the new QC method on AMSU-A radiance. In the new QC cases, as the contaminated data removed from the three-dimensional variational assimilation (3DVar), the tracks of both typhoons were much closer to the observations due to the increments of initial geopotential height and wind fields. In addition, the typhoons’ intensities were much closer to the observations with more reasonable temperature field for the warm structure of typhoon core development. In the original cases, with much more contaminated AMSU-A radiance in WRF, both typhoons’ tracks and intensities were much worse simulated. An improvement ratio to simulated track error was 12, that is an improvement to 540 km compared to the track without AMSU-A radiance assimilated, in the Kalmaegi case. And the ratio was 13 with 118 km improvement to simulated track in the Kompasu case.
MA Gang , WANG Yunfeng , ZHANG Xiaohui , GU Chengming , ZHONG Bo , GUO Xingliang . A quality control method based on gradient information of microwave radiation data AMSU-A[J]. Journal of Tropical Oceanography, 2017 , 36(2) : 86 -95 . DOI: 10.11978/2016049
Tab. 1 Threshold value of quality control based on AMSU-A gradient information along the scan line表1 AMSU-A资料基于沿扫描线方向梯度信息质量控制的阈值统计 |
卫星平台 | 通道 | 阈值 |
---|---|---|
NOAA-15 | 5 | 0.304 |
6 | 0.193 | |
7 | 0.207 | |
8 | 0.191 | |
9 | 0.164 | |
NOAA-16 | 5 | 0.432 |
6 | 0.231 | |
7 | 0.169 | |
8 | 0.236 | |
9 | 0.188 | |
NOAA-18 | 5 | 0.389 |
6 | 0.264 | |
7 | 0.283 | |
8 | 0.270 | |
9 | 0.187 |
Fig. 1 The mean gradient of all AMSU-A channels of NOAA-16 with BGI_QC and without BGI_QC图1 采用BGI_QC前后NOAA-16 AMSU-A通道的水平梯度信息的平均值 |
Fig. 2 CLW (a) and horizontal gradient anomalies with respect to brightness temperature of NOAA-18 AMSU-A along its scanning direction (b)图2 CLW分布(a)与NOAA-18 AMSU-A 通道5沿扫描方向的水平梯度距平分布(b) |
Fig. 3 CLW and brightness temperature with respect to channel 5 of NOAA-18 AMSU-A. Small circles indicate satellite data used in assimilation. Big red circle denotes the area used for comparison. a) Without BGI_QC; and b) with BGI_QC)图3 CLW分布情况和NOAA-18 AMSU-A5通道卫星亮温资料的分布 |
Tab. 2 Numerical experimental designs表2 试验方案设计 |
试验方案 | 形成模式初始场所用的资料 | 质量控制方法 |
---|---|---|
Ctrl | NCEP GFS | 没有QC |
Exp.1 | NCEP GFS +AMSU-A | WRFDA_QC |
Exp.2 | NCEP GFS + AMSU-A | BGI_QC_X + WRFDA_QC |
Fig. 4 Increment to wind field at 500 hPa between Exp.2 and Exp.1图4 Exp.2与Exp.1中的500hPa 风场增量分布 |
Fig. 5 Meridional section to increments between Exp.2 and Exp.1 along 21°18°N. a) Geopotential height (units: m); and b) temperature (units: K)图5 Exp.2与Exp.1的物理量增量沿21°18°N的经向垂直剖面 |
Fig. 6 Comparison of simulated tracks and observations for Typhoon Kalmaegi. a) Simulated typhoon tracks by all three experiments; and b) departures of the simulated tracks from observations图6 各试验方案模拟的台风预报路径情况与实况的对比 |
Fig. 7 Improvement to predicted typhoon track by Exp.2 with respect to Exp.1 for Typhoon Kalmaegi图7 Exp.2与Exp.1对台风路径预报的“改善比” |
Fig. 8 Increment to wind field at 500 hPa to Exp.2 and Exp.1图8 初始时刻Exp.2与Exp.1中的500hPa 风场增量分布 |
Fig. 9 Meridional sections to increments between Exp.2 and Exp.1 along 22°48°N. a) Geopotential height (units: m); and b) temperature (units: K)图9 Exp.2与Exp.1中的物理量增量沿22°48°N的经向垂直剖面 |
Fig. 10 Comparison of simulated tracks and observations for Typhoon Kompasu. a) Simulated typhoon tracks by all three experiments; and b) departures to the simulated tracks with respect to observations图10 各组试验模拟的台风路径与实况间的对比图(a)及其偏差情况(b) |
Fig. 11 Improvement of predicted typhoon tracks by Exp.2 to Exp.1 for Typhoon Kompasu图11 Exp.2与Exp.1预报路径误差的“改善比” |
The authors have declared that no competing interests exist.
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