两次强降水风暴双偏振参量特征分析

基于济南S波段双偏振多普勒天气雷达探测数据,结合探空和地面实况资料,对2019年同一区域两次强降水风暴双偏振参量特征进行分析。结果表明：1）两次对流性强降水发生在弱垂直风切变环境下,具有较强的对流有效位能,低层湿度较大,0 ℃层高度较高,利于短时强降水的产生。2）两次强降水风暴都具有低质心热带降水特征,45 dBZ以上的强回波区主要位于环境0 ℃层高度之下。3）风暴低层强回波区都对应大的差分反射率因子ZDR和比差分相位KDP,ZDR≥0.5 dB,KDP≥0.5°·km-1,相关系数CC≥0.95;反射率因子在50~54 dBZ之间,对应的KDP＞1.0°·km-1,CC≥0.97,ZDR适中,是两次强降水风暴导致高强度降水的主要双偏振参量特征。4）两次强降水风暴ZDR柱和KDP柱高度存在明显差异,7月27日强降水风暴前侧出现ZDR柱和KDP柱,高度接近-10 ℃层高度,8月10日强降水风暴ZDR柱和KDP柱略高于0 ℃层高度,ZDR柱高度对雷暴强度具有指示作用。     

基于X波段双偏振相控阵雷达的超级单体风暴观测分析

为了研究X波段双偏振相控阵雷达对超级单体风暴的探测能力,利用X波段双偏振相控阵雷达和S波段双偏振天气雷达资料,分析了一次发生在华南地区的超级单体风暴在成熟阶段的精细结构观测特征,结果表明：X波段双偏振相控阵雷达较高的时空分辨率有利于精细监测超级单体快速演变过程,但同时受衰减影响明显,超级单体核心区后侧出现明显的“V”型缺口;超级单体的低层观测到CC谷和ZDR弧,中层观测到ZDR环和CC环,高层高ZH区对应较小的ZDR和CC,这些都是超级单体发展旺盛的重要特征;垂直方向上观测到ZDR柱,ZDR柱与上升气流密切相关。降雹前ZDR柱迅速增加,冰雹降落后ZDR柱高度迅速降低。冰雹降落到地面后会部分融化,导致含水量显著增加,因此在近地层出现KDP大值区,冰雹与降水的混合相态则使得CC降低,这对冰雹的临近预警和识别冰雹在地面的降落位置具有很好的指示意义。研究结果可为X波段双偏振相控阵雷达在强对流天气监测预警中的应用提供参考。     

基于S波段双偏振雷达和X波段相控阵雷达的超级单体观测分析

利用广州S波段双偏振雷达和X波段相控阵雷达资料,对2022年3月26日一次降雹超级单体风暴成熟阶段的雷达观测特征开展分析,结果表明:超级单体呈现出钩状回波、回波悬垂、中气旋、三体散射等经典结构特征。径向速度上观测到中低层辐合、高层辐散以及中气旋和反气旋共存的双涡旋结构,有助于超级单体的维持发展。偏振特征分析发现,超级单体低层出现了反射率因子(ZDR)弧,低层强回波区对应偏小的差分反射率(ZDR)、低的相关系数(CC)和大的差分相移率(KDP),符合融化的冰雹特征。中层观测到ZDR环、CC环和三体散射(TBSS)的偏振特征。高层强回波区对应低的ZDR、较高的CC和低的KDP,对应空中干的大冰雹。垂直方向上观测到ZDR柱和KDP柱,ZDR柱最大发展高度达到8 km。X波段相控阵雷达更快的扫描速度还精细监测到超级单体钩状回波和中气旋的形成演变过程,低层也观测到与S波段双偏振雷达类似的ZDR弧特征和融化中的冰雹特征,但是使用中要留意衰减造成的影响。     

双偏振雷达在江苏“7.6”降雹过程中的应用分析

针对2019年7月6日发生在江苏徐州、宿迁、淮安、南京以及常州一线的一次大范围冰雹天气过程,利用再分析资料分析天气背景、不稳定机制和抬升条件。通过徐州和南京S波段双偏振雷达偏振参量及宿迁和淮安的双多普勒天气雷达风场反演技术对冰雹云的热动力结构和微物理特征开展了详细的分析。结果表明:此次大范围冰雹天气发生在高空冷涡南落、横槽南摆,低层暖湿气流北抬,上下层强烈不稳定的环流背景下,地面低压缓慢东移南压,提供了辐合抬升条件。此次降雹天气过程中,雷达回波图上显示有典型的冰雹云特征——三体散射长钉、回波穹隆结构、强度超过50 dBZ,中层径向辐合,风暴顶辐散等特征。双偏振雷达各偏振参量也表现出冰雹云的特点,出现冰雹的地区展现水平反射率因子ZH大、差分反射率因子ZDR小、相关系数CC小的特征,ZDR值为-1.0～0.5 dB,CC值小于0.85;超级单体在近地层还出现表征入流区的CC谷、ZDR柱、差分相移率KDP柱等特征。ZDR柱、KDP柱和CC谷等双偏振参量特征在强对流短时临近预报和冰雹识别方面具有很强的应用潜力。双雷达风场反演表明此次过程降雹集中时段,冰雹云的穹隆空间结构,降雹时刻存在的明显下沉气流。     

一次秋季冰雹过程的环境场和双偏振雷达特征分析

针对2021年9月20日浙江中部出现的一次冰雹天气过程，利用常规气象观测资料和NCEP GDAS/FNL 0.25°×0.25°再分析资料分析了环流背景、不稳定性和触发条件，通过金华S波段双偏振雷达对冰雹云的演变及其结构特征展开分析。结果表明:（1）降雹发生在西太平洋副热带高压东退、高空槽和低层低涡东移的环流背景下，大气呈现“上干冷、下暖湿”的对流性不稳定层结，近地面中尺度辐合线提供了辐合抬升条件，是一次准正压类强对流天气。（2）超级单体风暴具备典型的冰雹云特征，回波强度超过55 dBZ、异常大的垂直累积液态水含量、三体散射长钉、风暴顶辐散等均对冰雹天气预警有较好的指示意义。（3）超级单体成熟阶段基本反射率因子≥55 dBZ区域的差分反射率因子ZDR为负（极值达-2.12 dB）、差分相移率KDP出现“空洞”现象、相关系数CC低于0.9指示出现了大的干冰雹。（4）ZDR柱（>1 dB）伸展的高度与上升气流存在正相关，ZDR柱伸展到-20 ℃层以上有利于雹胚的生成以及冰雹增长，可作为判别对流风暴能否降雹的指标之一，ZDR柱演变规律在短临预报以及冰雹识别方面具有较好的应用潜力。     

一次超级单体引发的秋季特大冰雹和龙卷雷达探测分析

利用烟台S波段双偏振多普勒雷达和荣成CINRAD/SA新一代天气雷达探测数据,结合探空、地面气象观测、ERA5再分析和冰雹、龙卷实地调查等资料,对2021年10月1日在山东半岛东部烟台、威海发生的特大冰雹和龙卷风暴的天气形势、环境参量和雷达探测特征进行分析。主要结果为：与气候平均场相比,造成本次强对流过程的500hPa东北冷涡异常强盛,850hPa自华南到东北地区西部有持续偏南水汽输送;在此异常环流背景下,山东半岛东部具有上干冷下暖湿、强的0～6km垂直风切变和对流有效位能等有利于强冰雹、龙卷发生的环境条件;近地面的风暴前低压、雷暴高压和冷池特征明显。降雹时的风暴呈现典型超级单体特征,低层具有明显的钩状回波和倒“V”字型前侧入流缺口,垂直剖面显示出明显的有界弱回波区、差分反射率柱（ZDR柱）特征;根据大冰雹落点和降雹开始时间等信息,统计对应雹云的反射率因子、ZDR、相关系数（CC）的中位数分别为48.7dBz、0.89dB和0.90;地面出现龙卷和大冰雹时,风暴顶辐散强度最大达到71.5m·s-1。后侧阵风锋对应的出流边界北端的偏北气流与风暴前侧的偏南气流形成强涡旋上升运动,导致EF1级龙卷产生;龙卷发生在钩状回波的顶端,大冰雹多出现在入流缺口的北侧。地面发现龙卷发生前约5min,雷达探测到龙卷碎片特征,ZDR和CC分别最低至-0.1dB和0.81;龙卷发生前约11min,探测到风暴低层的ZDR弧和风暴右后侧的下沉反射率因子核特征;荣成、烟台雷达分别提前22min、5min识别出中气旋和龙卷涡旋,可为龙卷预警提供重要参考。基于观测分析,给出了本次超级单体风暴的低层流场及龙卷、大冰雹落区的示意图。     

北京强对流天气中X波段双偏振雷达特征及应用

针对2018年夏季北京15次强对流天气过程,利用房山单站X波段双偏振雷达与北京观象台S波段天气雷达探测产品进行对比分析,探讨新探测手段的应用价值。结果表明：相对于常规天气雷达来说,双偏振雷达在粒子识别方面具有明显优势,成为冰雹等天气监测、预报预警的强有力手段。在冰雹识别上,X波段双偏振雷达的差分反射率因子（ ZDR）和相关系数（ρhv ）是两个重要的偏振量,ZDR 较小,接近0,有时为负值; ρhv小于0.9。在强降水识别方面, ZDR大值和差分传播相移率（KDP ）能够较好地指示雨强较大的降水。低仰角的 ZDR达5dB以上,KDP 在8°/km以上, ρhv达0.95以上时,地面5分钟雨量可达到或超过10mm。两种雷达的对比分析来看,反射率因子强度（R）、垂直累积液态水含量（VIL）均较SA天气雷达强度偏强。此外,由于X波段雷达波长较短,单部雷达的探测波束经过强降水区会发生比较严重的电磁衰减,致使强降水后部的降水回波强度偏弱,严重影响预报员对降水强度和降雨持续时间的判断,需要与SA天气雷达配合使用或者利用多部X波段雷达组网进行强降雨的监测分析。     

辽宁营口2019-08-16龙卷过程双偏振雷达特征分析

利用MICAPS、自动站和双偏振雷达资料,分析营口2019年8月16日龙卷天气过程。发现此次龙卷天气在高空低涡的天气背景下发生,高层冷平流与低层暖平流叠加,积累了充分的不稳定能量,为龙卷的发生提供了潜势;温度层结曲线与露点温度曲线呈“X”型,有利于雷暴大风生成。雷达图上南北两条窄带回波相遇是雷暴的触发条件;产生龙卷的雷暴单体强回波区域向下延伸指示了雷暴的发展情况,反射率图上高层强回波悬垂、低层弱回波区、钩状回波预示着该风暴为强风暴;径向速度产品图上表征气旋式旋转的正负速度对的发展变化可以指示龙卷的位置和强度,05°仰角上辐散区可以确定地面大风的发生时间和位置;相关系数CC产品、差分反射率ZDR产品、差分相移率KDP产品等偏振量有利于确定龙卷的影响范围;粒子分类产品对冰雹落地时间有较好的指示。     

贵州北部一次冰雹天气的双偏振特征分析

该文利用务川C波段双偏振雷达和常规资料分析了2021年3月30日贵州西北部一次冰雹天气的成因和偏振参量特征。研究表明,当日贵州处于低层气旋性切变和高层强正涡度平流区域内,贵州东北部有中等到强的垂直风切变,且发现干舌与地面辐合线相交处有利于激发强烈的上升气流。强回波成熟阶段,最大水平反射率因子达到70 dBz,并出现钩状回波、三体散射长钉、有界弱回波区和回波悬垂现象。偏振参量分析表明,此次过程出现冰雹时,Z_H值在60 dBz以上,ZDR值较低在-2~1.75 dB,对于湿冰雹Z_DR值偏高在3~6 dB,K_DP值在0 dB左右,伴有强降水时K_DP值较大在2~6 °/km,CC值较低在0.85~0.93。在湿球0 ℃高度以上出现了伴随强上升气流的Z_DR柱和K_DP柱。三体散射长钉在Z_DR和CC图中有很好的体现,且CC图中还出现非均匀波束充塞现象。     

温州“4·24”一次冰雹天气特征分析

采用NCEP分析资料、常规高空地面观测资料、温州双偏振雷达资料等,分析了2019年4月24日(简称“4·24”)发生在温州地区的一次冰雹天气过程。结果表明:在高空槽东移过程中,弱冷空气影响配合低层切变线和低空急流,造成了此次强对流天气过程的发生;午后对流条件良好,冰雹发生前,低层有高能舌伸向温州地区,中层有北方干冷空气南下,二者叠加造成强烈的不稳定层结,同时低层辐合、高层辐散,上升运动强烈,为冰雹的产生提供了良好的动力条件;中β尺度的强对流单体内部形成-60℃的对流核,冷中心位于整个云团TBB梯度最大的地方,位置与短时强降水、雷雨大风、局地冰雹等强对流天气的发生区域有较好的对应;利用VIL、Z、ZDR和KDP可以综合分析冰雹,其回波特征为:降雹前VIL值均有明显的跃增现象;>60 dBZ的强回波区对应的ZDR有明显的负值区,ZDR一般为-4~0 dB;对于较大的冰雹,>60 dBZ的强回波区对应KDP出现“空洞”区。     

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959–2014

The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics.     

Could the Recent Taal Volcano Eruption Trigger an El Ni?o and Lead to Eurasian Warming?

正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment.     

VARIABILITY OF INTER-ANNUAL RELATIONSHIP BETWEEN INDIAN OCEAN DIPOLE AND HUAXI REGION’S AUTUMN PRECIPITATION

The moving-window correlation analysis was applied to investigate the relationship between autumn Indian Ocean Dipole (IOD) events and the synchronous autumn precipitation in Huaxi region, based on the daily precipitation, sea surface temperature (SST) and atmospheric circulation data from 1960 to 2012. The correlation curves of IOD and the early modulation of Huaxi region’s autumn precipitation indicated a mutational site appeared in the 1970s. During 1960 to 1979, when the IOD was in positive phase in autumn, the circulations changed from a “W” shape to an ”M” shape at 500 hPa in Asia middle-high latitude region. Cold flux got into the Sichuan province with Northwest flow, the positive anomaly of the water vapor flux transported from Western Pacific to Huaxi region strengthened, caused precipitation increase in east Huaxi region. During 1980 to 1999, when the IOD in autumn was positive phase, the atmospheric circulation presented a “W” shape at 500 hPa, the positive anomaly of the water vapor flux transported from Bay of Bengal to Huaxi region strengthened, caused precipitation ascend in west Huaxi region. In summary, the Indian Ocean changed from cold phase to warm phase since the 1970s, caused the instability of the inter-annual relationship between the IOD and the autumn rainfall in Huaxi region.     

ANALYSIS OF “BIMODAL PATTERN” STORM ACTIVITY CHARACTERISTICS OF THE BAY OF BENGAL

Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms.     

LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN

Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d.     

AN ATTRIBUTION ANALYSIS OF CHANGES IN POTENTIAL EVAPOTRANSPIRATION IN THE BEIJING–TIANJIN–HEBEI REGION UNDER CLIMATE CHANGE

Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region.     

Revisiting the Concentration Observations and Source Apportionment of Atmospheric Ammonia

正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on     

全球贸易隐含碳变化及其影响分析

基于最新的GTAP8 (Global Trade Analysis Project）数据库,使用投入产出法,分析了2004年到2007年全球贸易变化下南北集团贸易隐含碳变化及对全球碳排放的影响。结果显示,随着发展中国家进出口规模扩张,全球贸易隐含碳流向的重心逐渐向发展中国家转移。2004年到2007年,发达国家高端设备制造业和服务业出口以及发展中国家资源、能源密集型行业及中低端制造业出口的趋势加强,该过程的生产转移导致全球碳排放增长4.15亿t,占研究时段全球贸易隐含碳增量的63%。未来发展中国家的出口隐含碳比重还将进一步提高。贸易变化带来的南北集团隐含碳流动变化对全球应对气候变化行动的影响日益突出,发达国家对此负有重要责任。     

COMPARATIVE ANALYSIS OF VARIOUS DATA OF AIR–SEA TEMPERATURE DIFFERENCE AND ITS VARIATION ACROSS SOUTH CHINA SEA IN THE PAST 35 YEARS

Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter.     

Retrieval of outgoing longwave radiation from COMS narrowband infrared imagery

Hourly outgoing longwave radiation(OLR) from the geostationary satellite Communication Oceanography Meteorological Satellite(COMS) has been retrieved since June 2010. The COMS OLR retrieval algorithms are based on regression analyses of radiative transfer simulations for spectral functions of COMS infrared channels. This study documents the accuracies of OLRs for future climate applications by making an intercomparison of four OLRs from one single-channel algorithm(OLR12.0using the 12.0 μm channel) and three multiple-channel algorithms(OLR10.8+12.0using the 10.8 and 12.0 μm channels; OLR6.7+10.8using the 6.7 and 10.8 μm channels; and OLR All using the 6.7, 10.8, and 12.0 μm channels). The COMS OLRs from these algorithms were validated with direct measurements of OLR from a broadband radiometer of the Clouds and Earth's Radiant Energy System(CERES) over the full COMS field of view [roughly(50°S–50°N, 70°–170°E)] during April 2011.Validation results show that the root-mean-square errors of COMS OLRs are 5–7 W m-2, which indicates good agreement with CERES OLR over the vast domain. OLR6.7+10.8and OLR All have much smaller errors(～ 6 W m-2) than OLR12.0and OLR10.8+12.0(～ 8 W m-2). Moreover, the small errors of OLR6.7+10.8and OLR All are systematic and can be readily reduced through additional mean bias correction and/or radiance calibration. These results indicate a noteworthy role of the6.7 μm water vapor absorption channel in improving the accuracy of the OLRs. The dependence of the accuracy of COMS OLRs on various surface, atmospheric, and observational conditions is also discussed.