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降雨导致的海面粗糙度对Aquarius卫星盐度反演的影响研究
MAWentao, YANGXiaofeng, YUYang, LIUGuihong, LIZiwei, JINGCheng
2015, 34(7): 89-96. doi: 10.1007/s13131-015-0660-5
关键词: Aquarius, 盐度遥感, 降雨, L波段, 发射率
降雨引起海表面L波段发射率变化的原因主要有2种, 即表层海水淡化和海表粗糙度改变。通过对Aquarius与TRMM 3B42的匹配数据集研究发现, 与模式得到的盐度相比, Aquarius卫星反演得到的盐度在降雨发生, 尤其是高降雨率时明显降低。在降雨率为25 mm/hr时, 卫星反演的盐度比模式盐度平均低约2 psu。当不考虑海水淡化的影响时, 考虑海表面粗糙度的影响时可以消除反演得到的盐度与模式盐度的偏差。将降雨波谱引入小斜率近似模型, 可以模拟海表面粗糙度的改变, 进而得到降雨引起的海表面发射率改变。本文比较了经验的和理论的降雨波谱模型, 发现采用经验模型可以更好地模拟实测海面发射率增量, 然而经验模型的系数还需进一步改进。本文利用2年实测匹配数据对经验模型的系数进行拟合, 获得了降雨条件下海面发射率的改进模型。模型和实测数据表明, 海表发射率随风速和降雨率升高, 海表面发射率随降雨率的增长速度在低风速和低降雨率时较快, 而在高风速和大降雨率时较慢。改进模型得到的发射率增量与实测发射率增量的偏差在1e-4左右, 均方根误差略大于1e-3。最后, 本文利用2014年5月的匹配数据对模型进行了验证。结果表明, 采用改进模型反演得到的盐度与模式盐度的偏差得到了校正, 它们之间的均方根误差也减小了, 在低风速和低降雨率时均方根误差优于1 psu。
Improving the wind and wave estimation of dual-frequency altimeter JASON1 in Typhoon Shanshan and considering the rain effects
YANGLe, LINMingsen, ZOUJuhong, LIZhenghua, PANDelu
2008(5): 49-62.
关键词: altimeter, waveform, typhoon, rain, highwindspeed
Altimetry data have been widely used in various fields of oceanography, including the extreme weather events such as tropical cyclones, typhoons, and hurricanes. The performance of JASON1 in Typhoon Shanshan is assessed by examining the sensor geophysical data record and illustrates how the measured return waveform, significant wave height, and backscatter are all affected by various factors associated with the typhoon, with details by the rain are illustrated. The correction method to maintain accurate wave height and wind speed measurements in Typhoon Shanshan and the results are presented. Furthermore, the additional results of rain rate and typhoon eye diameter can be retrieved. Because of the lack of in-situ measurements of wind, wave, and rain rate at Typhoon Shanshan, results are compared with the forecasted typhoon data and a good agreement is found.
HY-2微波辐射计降雨条件下海面风速反演算法研究
王进, 张杰, 王晶
2017, 36(7): 32-38. doi: 10.1007/s13131-017-1080-5
关键词: HY-2微波辐射计, 降雨, 风速, 反演算法, 亮温
由于降雨改变了海洋-大气的辐射/散射特性,长期以来星载遥感器在降雨条件下进行海面风速信息提取存在困难。本文针对自主海洋动力环境卫星海洋2号(HY-2)搭载的扫描微波辐射计,分析了不同频段亮温对降雨和海面风速敏感性,自此基础上获得了一种对降雨不敏感的亮温通道组合,该亮温通道组合对海面风速的敏感性甚至高于原有亮温通道。本文利用该亮温通道组合建立了降雨条件下的风速反演算法,并将反演结果与WindSat全天候风速产品、HY-2微波辐射计原有风速产品以及浮标实测数据进行了比较。结果表明本文算法在降雨条件下的反演误差小于2m/s,明显优于原有HY-2微波辐射计风速产品,验证了本文发展的算法在降雨条件下的风速反演能力。
星载SAR对雨团催生海面风场的观测研究
叶小敏, 林明森, 袁新哲, 丁静, 解学通, 张毅, 徐莹
2016, 35(9): 80-85. doi: 10.1007/s13131-016-0936-4
关键词: 雨团, 合成孔径雷达, 海面风场, 下沉气流
雨团或对流雨是热带与亚热带地区的主要降雨形式,较易被高分辨率星载合成孔径雷达(SAR)探测到。SAR图像上的雨团足印是由大气中雨滴的散射与吸收、下沉气流等共同导致形成的。本文以RADARSAT-2卫星100 m分辨率的SAR图像上雨团引起的海面风场及其结构反演与解译作为实例进行分析。使用CMOD4地球物理模式函数,分别以NCEP再分析数据、欧洲MetOp-A卫星先进散射计(ASCAT)和中国HY-2卫星微波散射计的风向为外部风向,进行了SAR图像的海面风场反演。反演的海面风速相对于NCEP、ASCAT和HY-2的均方根误差(RMSE)分别为1.48 m/s,1.64 m/s和2.14 m/s。SAR图像上一侧明亮另一侧昏暗的圆形信号图斑被解译为雨团携带的下沉气流对海面风场(海面粗糙度)的改变所致。平行于海面背景风场其通过雨团圆形足印中心的剖面上的风速变化可拟合为正弦或余弦曲线,其拟合线性相关系数均不低于0.80。背景风场的风速大小、雨团引起的风速大小以及雨团足印的直径可利用拟合曲线获得,雨团足印的直径大小一般为数千米或数十千米,本文的8例个例解译与分析均验证了该结论。
台风中降雨对中国高分3号合成孔径雷达观测信号的影响
史剑, 胡佳臣, 邵伟增, 王小青, 袁新哲, 赵良波, 李晓峰
2019, 38(11): 121-133. doi: 10.1007/s13131-019-1502-7
关键词: Gaofen-3, 合成孔径雷达, 台风
中国民用c波段合成孔径雷达(SAR)高分-3(GF-3)于2016年8月投入使用。值得注意的是,在过去两年的任务中,几架GF-3在中国海域附近捕获了台风。本文对全球观测(GLO)和宽扫描sar (WSC)模式下垂直垂直(VV)偏振通道的六幅图像进行了研究。这项工作重点是调查使用GF-3 SAR观测降雨。这些图片配风从欧洲中期天气预报中心(ECMWF),有效波高的模拟WAVEWATCH-III (WW3)模型,海洋表面电流从气候预测系统版本2(CFSv2)国家环境预报中心(NCEP)和降雨率的数据热带降雨测量任务(TRMM)卫星。将海面粗糙度与SAR观测的归一化雷达截面(NRCS)进行比较,相关性为0.8。分析了模型模拟的NRCS与sar实测NRCS之间的差异对TRMM降雨速率和ww3模拟的显著波高的依赖关系。It发现雨的影响SAR抑制雷达信号的入射角度范围从15°到30°,虽然提高了雷达信号入射角度范围从30°到45°和入射角度小于10°.这一行为与以往的研究相一致,并有望为GF-3 SAR提供一种雨率检索算法。
An improved QuikSCAT wind retrieval algorithm and eye locating for typhoon
ZHONGJian, FEIJianfang, HUANGSixun, DUHuadong, ZHANGLiang
2012(1): 41-50. doi: 10.1007/s13131-012-0174-3
关键词: scatterometer, radiativetransfermodel, typhoonwindfield, locatingtheeyeoftyphoon
This paper proposes a rain considered geophysical model function (GMF), to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on radar signal considered. Combined with the NSCAT2 GMF and the rain correction model, the GMF plus Rain model is used to retrieve the ocean wind vectors from the collocated QuikSCAT and SSM/I rain rate data for typhoon Melor. The resulting wind speed estimates of typhoon Melor show improved agreement with the wind fields derived from the best track analysis of Japan Meteorological Agency (JMA). The results imply that compared with the GMF model, the GMF plus Rain model can improve the precision of wind retrieval under the rain condition. Then, a new general algorithm of locating the eye of typhoon through the normalized radar cross section (NRCS) is proposed. The implementation of this algorithm in the ten QuikSCAT observations of typhoon Melor suggests that this algorithm is effective.
台风条件下改进的Jason-1海面风速反演算法
QINBangyong, ZHOUXuan, ZHANGHonglei, YANGXiaofeng, LURong, YUYang, SHILijian
2014, 33(7): 83-88. doi: 10.1007/s13131-014-0500-z
关键词: 高度计, 风速, 降雨影响, 热带气旋
台风条件下现场观测资料十分稀少,Young等人、Gu等人利用台风模式风速代替现场观测数据,通过与高度计观测的后向散射截面进行对比分析,建立高风速反演算法。但台风模式自身的缺陷,以及降雨的衰减、体后向散射和雨表面扰动作用,影响了这些算法的精度。HRD海面风速再分析数据融合了所有的现场观测数据,其精度明显优于台风模式风速数据。为了改进台风条件下海面风速反演算法的精度,本文首先利用CMORPH降雨数据和降雨订正模型对Jason-1后向散射截面进行降雨订正,并通过HRD海面风速再分析数据代替台风模式风速数据建立匹配数据集,推导高度计在无雨、高风速条件下海面风速反演算法;然后,利用无雨条件下C和Ku波段高度计后向散射截面的关系,给出了台风条件下海面风速反演的技术流程;最后,利用Irene飓风对本文算法进行了验证,试验结果表明,本文算法在C和Ku波段的均方根误差分别为1.99和2.75m/s,精度明显优于Gu算法和Jason-1业务化算法,且C波段比Ku波段更适合台风条件下海面风速的反演。
PROBLEMS OF ASSESSING MARINE POLLUTION
R.B.CLARK, 张松龄
1985(3): 453-462.
The sea receives an enormous variety of wastes from direct discharges or, indirectly, from rivers or by rain or precipitation from the atmosphere.In some areas, toxic wastesaccumulate in sufficient quantity to create a threat to human health or to damagefisheries or other natural resources.It is necessary to be able to measure the effects ofpollution in the sea.This paper is concerned with the problems of assessing the impactof marine pollution on biological systems.
Rainfall effect on wind waves and the turbulence beneath air-sea interface
ZHAODongliang, MAXin, LIUBin, XIELian
2013, 32(11): 10-20. doi: 10.1007/s13131-013-0372-7
关键词: rainfall, windwave, waveage, turbulence, turbulentkineticenergy
Rainfall effects on wind waves and turbulence are investigated through the laboratory experiments in a large wind-wave tank. It is found that the wind waves are damped as a whole at low wind speeds, but are enhanced at high wind speeds. This dual effect of rain on the wind waves increases with the increase of rain rate, while the influence of rainfall-area length is not observable. At the low wind speed, the corresponding turbulence in terms of the turbulent kinetic energy (TKE) dissipation rate is significantly enhanced by rainfall as the waves are damped severely. At the high wind speed, the augment of the TKE dissipation rate is suppressed while the wind waves are enhanced simultaneously. In the field, however, rainfall usually hinders the development ofwaves. In order to explain this contradiction of rainfall effect on waves, a possibility about energy transfer fromturbulence to waves in case of the spectral peak ofwaves overlapping the inertial subrange of turbulence is assumed. It can be applied to interpret the damping phenomenon of gas transfer velocity in the laboratory experiments, and the variation of the TKE dissipation rates near sea surface compared with the law of wall.
基于TRMM观测的亚洲——太平洋三个季风区的降水结构特征
LIJiangnan, ZHENGYanping, LIFangzhou, GUOFeiyun, LIWeibiao
2014, 33(3): 111-117. doi: 10.1007/s13131-014-0417-6
关键词: 降水, 三维结构, 亚洲——太平洋季风区, TRMM
利用热带测雨卫星(TRMM)10年的探测结果,对亚洲—太平洋三个季风区(东亚季风区、西北太平洋季风区和印度季风区)降水的三维结构及潜热廓线特征进行了分析。结果表明:(1)东亚季风区的对流降水量和层云降水量百分比的季节变化最明显,印度季风区次之,西北太平洋季风区最小。东亚季风区层云降水与对流降水间的关系四季变化较大,西北太平洋季风区和印度季风区四个季节的层云降水均大于对流降水。(2)三个季风区四种水粒子的垂直廓线有明显差异,云冰在5KM以上随高度先增后减,在9KM左后其值达到最大;云水在垂直方向上的分布与云冰相反,其最大值在3至4KM左右。可降冰与云冰具有相似的垂直廓线,但可降冰的大值区主要在4至9KM,云冰则在7至16KM,且可降冰的量级要大于云冰。可降水粒子主要集中在4KM以下,地面至2KM之间其含量最大。(3)印度季风区的云冰含量由春至冬变化最明显,其他两个地区变化较小;而四个季节西北太平洋的云水含量始终高于其他两个地区。(4)潜热廓线都有相似的双峰结构,第一峰值在4KM高度,第二峰值在2KM高度。春夏两季三个区的潜热差别不大,秋冬两季西北太平洋高于其它两区;三个区均在夏秋两季潜热释放量较大,春冬两季较小。
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