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1.
Quantifying the radiative forcing due to aerosol–cloud interactions especially through cirrus clouds remains challenging because of our limited understanding of aerosol and cloud processes. In this study, we investigate the anthropogenic aerosol indirect forcing (AIF) through cirrus clouds using the Community Atmosphere Model version 5 (CAM5) with a state-of-the-art treatment of ice nucleation. We adopt a new approach to isolate anthropogenic AIF through cirrus clouds in which ice nucleation parameterization is driven by prescribed pre-industrial (PI) and presentday (PD) aerosols, respectively. Sensitivities of anthropogenic ice AIF (i.e., anthropogenic AIF through cirrus clouds) to different ice nucleation parameterizations, homogeneous freezing occurrence, and uncertainties in the cloud microphysics scheme are investigated. Results of sensitivity experiments show that the change (PD minus PI) in global annual mean longwave cloud forcing (i.e., longwave anthropogenic ice AIF) ranges from 0.14 to 0.35 W m–2, the change in global annual mean shortwave cloud forcing (i.e., shortwave anthropogenic ice AIF) from–0.47 to–0.20 W m–2, and the change in net cloud forcing from–0.12 to 0.05 W m–2. Our results suggest that different ice nucleation parameterizations are an important factor for the large uncertainty of anthropogenic ice AIF. Furthermore, improved understanding of the spatial and temporal occurrence characteristics of homogeneous freezing events and the mean states of cirrus cloud properties are also important for constraining anthropogenic ice AIF. 相似文献
2.
用TRMM/TMI估算HUBEX试验区的云中液态水 总被引：4，自引：3，他引：4
文中应用热带降雨测量卫星微波成像仪的微波遥感资料反演云中液态水。由于微波成像仪85.5 GHz通道对云中液态水非常敏感,通过离散纵坐标矢量辐射传输模式,运用迭代的方法可以有效地反演出陆地上空非降水云中的液态水路径。在淮河流域能量与水分循环试验中,分别运用微波成像仪85.5 GHz垂直极化单通道和微波成像仪85.5 GHz极化亮温差两种方法来估算陆地上空的云中液态水路径,反演结果与地基微波辐射计的测量结果是较为一致的。当地表比辐射率或地表温度误差较大时,用极化亮温差法估算云中液态水路径相对较好,尤其是对于低云,因为该方法对地表温度不敏感。 相似文献
3.
云检测是卫星资料同化的重要前处理步骤,无论是晴空资料同化还是有云资料同化,都需要准确地区分有云和晴空资料。由于陆地地表发射率的多变性和微波能穿透部分云类的特点,微波湿度计资料在陆地上空的云检测研究一直是难点。利用快速辐射传输模式（CRTM）分析了不同云类条件下FY-3C微波湿度计（MWHS-Ⅱ）各通道亮温的通道间变率特征,根据MWHS-Ⅱ亮温通道间变率随云高以及云中液态水含量的增大而减小的特点,提出了一个基于亮温通道变率的MWHS-Ⅱ陆地资料云检测方法。与已有的云产品比较结果表明:新的云检测算法能有效地剔除大部分受云影响的资料,剔除后的晴空资料观测和模拟偏差更好地符合高斯分布。新方法对过冷水云、冰云、重叠云的检测能力较强,正确检测率可以达到80%,对卷云以及高度较低的水云的检测能力相对较弱。新方法能有效利用MWHS-Ⅱ观测资料自身完成云检测,在MWHS-Ⅱ资料同化中有很好的应用前景。 相似文献
4.
利用2007~2010年北半球夏季（6~8月）CloudSat卫星搭载的云廓线雷达（Cloud Profile Radar,CPR）探测结果对0°~60°N区域单层、双层和三层云系的水平分布、垂直结构特征及各云层云类组成、云水路径等物理量分布进行分析。云量的统计结果表明CPR探测的单层、双层和三层云系的云量分别为36.63%、8.26%和1.40%,云量的水平分布表明其高值区主要位于对流旺盛区域,且高值区的云层云顶高、厚度大,而低值区则多位于副热带高压区域。对不同云类的出现频率统计分析结果表明,单层云系中各云类的出现频率相近;多层云系的上层以卷云为主,下层以层积云为主。对比海陆差异发现洋面卷云和层积云的出现频率显著高于陆面,但高层云和高积云的出现频率低于陆面。云水路径分析表明,单层云系的冰水路径和液水路径均最大,而在多层云系中云层越高、厚度越大、冰水路径越大,液水路径则随着云层的降低增大。 相似文献
5.
The Microwave Radiation Imager (MWRI) on board Chinese Fengyun-3 (FY-3) satellites provides measurements at 10.65, 18.7, 23.8, 36.5, and 89.0 GHz with both horizontal and vertical polarization channels. Brightness temperature measurements of those channels with their central frequencies higher than 19 GHz from satellite-based microwave imager radiometers had traditionally been used to retrieve cloud liquid water path (LWP) over ocean. The results show that the lowest frequency channels are the most appropriate for retrieving LWP when its values are large. Therefore, a modified LWP retrieval algorithm is developed for retrieving LWP of different magnitudes involving not only the high frequency channels but also the lowest frequency channels of FY-3 MWRI. The theoretical estimates of the LWP retrieval errors are between 0.11 and 0.06 mm for 10.65- and 18.7-GHz channels and between 0.02 and 0.04 mm for 36.5- and 89.0-GHz channels. It is also shown that the brightness temperature observations at 10.65 GHz can be utilized to better retrieve the LWP greater than 3 mm in the eyewall region of Super Typhoon Neoguri (2014). The spiral structure of clouds within and around Typhoon Neoguri can be well captured by combining the LWP retrievals from different frequency channels. 相似文献
6.
Retrieval of Liquid Water Path Inside Nonprecipitating Clouds Using TMI Measurements 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Quantitative estimates of liquid water path （LWP） in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship between microwave brightness temperature （TB） and LWP in the nonprecipitating clouds is studied by using satellite microwave measurements from the TRMM Microwave Imager （TMI） onboard the Tropical Rainfall Measuring Mission （TRMM）, together with a radiative transfer model for microwave radiance calculations. Radiative transfer modeling shows that the sensitivity is higher at both 37.0- and 85.5-GHz horizontal polarization channels for the LWP retrievals. Also, the differences between the retrieved values responding to TBs of various channels and the theoretical values are displayed by the model. Based upon above simulations, with taking into account the factor of resolution and retrieval bias for a single,channel, a nonprecipitating cloud LWP in the summer subtropical marine environment retrieval algorithm is formulated by the combination of the two TMI horizontal polarization channels, 37.0 and 85.5 GHz. Moreover,by using TMI measurements （1Bll）, this algorithm is applied to retrieving respectively LWPs for clear sky, nonprecipitating clouds, and typhoon precipitating clouds. In the clear sky case, the LWP cl~anges from -1 to 1 g m-2, and its mean value is about 10^-5 g m^-2. It indicates that, using this combination retrieval algorithm, there are no obvious systemic deviations when the LWP is low enough. The LWP values varying from 0 to 1000 g m^-2 in nonprecipitating clouds are reasonable, and its distribution pattern is very similar to the detected results in the visible channel of Visible and Infrared Scanner （VIRS） on the TRMM. In typhoon precipitating clouds, there is much more proportion of high LWP in the mature phase than the early stage. When surface rainfall rate is lower than 5 mm h^-1, the LWP increases with increasing rainfall rate. 相似文献
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8.
Two-moment bulk stratiform cloud microphysics in the grid-point atmospheric model of IAP LASG (GAMIL) 总被引：1，自引：0，他引：1
A two-moment bulk stratiform microphysics scheme, including recently developed physically-based droplet activation/ice nucleation parameterizations has been implemented into the Grid-point Atmospheric Model of IAP LASG (GAMIL) as an effort to enhance the model’s capability to simulate aerosol indirect effects. Unlike the previous one-moment cloud microphysics scheme, the new scheme produces a reasonable representation of cloud particle size and number concentration. This scheme captures the observed spatial variations in cloud droplet number concentrations. Simulated ice crystal number concentrations in cirrus clouds qualitatively agree with in situ observations. The longwave and shortwave cloud forcings are in better agreement with observations. Sensitivity tests show that the column cloud droplet number concentrations calculated from two different droplet activation parameterizations are similar. However, ice crystal number concentration in mixed-phased clouds is sensitive to different heterogeneous ice nucleation formulations. The simulation with high ice crystal number concentration in mixed-phase clouds has less liquid water path and weaker cloud forcing. Furthermore, ice crystal number concentration in cirrus clouds is sensitive to different ice nucleation parameterizations. Sensitivity tests also suggest that the impact of pre-existing ice crystals on homogeneous freezing in old clouds should be taken into account. 相似文献
9.
为了发展云雷达与微波辐射计联合反演液态水含量的方法, 利用2019年4—9月中国气象科学研究院在广东龙门开展的综合观测试验中的双波段云雷达和微波辐射计数据, 首先检验了在降水条件下微波辐射计天顶观测和斜路径观测两种探测模式反演温度(T)、相对湿度(RH)、液态水含量(LWC)和液态水路径(LWP)的合理性, 然后分析了两种探测设备反演LWC和LWP的差别。得到以下结论: (1)微波辐射计在斜路径观测模式下反演的产品受降水影响较小, 其反演结果明显优于天顶观测模式; (2)两种探测设备反演的LWP相关性较好且随时间变化较为一致, 但云雷达反演LWP与平均回波强度有明显相关, 随着雷达回波强度的增大, 云雷达与微波辐射计反演的LWP之比越大; (3)两种探测设备反演的LWC相关性较差且存在明显偏差, 在不考虑融化层的情况下单波段云雷达反演LWC与微波辐射计随高度变化趋势相近, 双波段云雷达反演LWC与微波辐射计反演结果在1 km及其以上区间存在明显差异。 相似文献
10.
Atmospheric back radiation in the tropical pacific: Intercomparison of in-situ measurements, simulations and satellite retrievals 总被引：1，自引：0，他引：1
Summary The back radiation has been measured with an Eppley pyrgeometer on board the R/V Vickers in the tropical Pacific Ocean during the field campaigns COARE (Coupled Ocean Atmosphere Response Experiment) and CEPEX (Central Equatorial Pacific Experiment) in February and March 1993, respectively. As part of these compaigns radiosondes have been launched from the Vickers several times per day and cloud cover was observed frequently. The radiosonde and cloud observations are used together with a radiative transfer model to calculate the back radiation for a subsequent intercomparison with the pyrgeometer measurements. Another means of comparison is derived from space-borne SSM/I (Special Sensor Microwave/Imager) measurements. The mean difference between pyrgeometer measurements and simulated downwelling irradiance at the sea surface is less than 2 W/m2, at a mean of 425 W/m2 in the warm pool, with a standard deviation of 8 W/m2. The comparison of satellite measurements with pyrgeometer readings shows a mean difference of-3 W/m2 and a standard deviation of 14 W/m2. The mean difference between satellite-derived back radiation and simulated one is 3 W/m2 with a standard deviation of 14 W/m2. Comparisons with results obtained from bulk formulae applied to surface meteorological observations show a good performance of the bulk parameterisations in the cloud-free case but a general overestimation of the back radiation in cloudy situations.With 5 Figures 相似文献
11.
STUDIES OF THE VERTICAL STRUCTURE MODEL AND THE MICROWAVE ATTENUATION OF CLOUDS AND PRECIPITATION OVER TROPICAL OCEAN AREA 下载免费PDF全文
下载免费PDF全文 Using radiosonde data and other related observations in the TOGA-COARE IOP(fromNovember 1,1992 to February 28,1993),the microwave attenuation of non-precipitating clouds isinvestigated based on microwave radiative transfer model(MRTM)at the specific frequencies of6.8,10.65,13.9,19.35,22.235,37.0,85.5 and 90.0 GHz.Besides,utilizing the data of theairborne radar and radiometer at 13.8 GHz in the IOP(Intensive Observation Period),verticalstructure models for different types of precipitating clouds are obtained,and also the microwaveattenuation of precipitating cloud is studied.Some statistical characteristics of 13.8 GHzmicrowave path integrated attenuation for stratiform and convective precipitating clouds arepresented.The results given here are valuable for the spaceborne microwave remote sensing ofprecipitation,and the cloud and precipitation attenuation corrections in the spaceborne microwaveremote sensing of earth surface over tropical ocean area. 相似文献
12.
Man–computer interactive method on cloud classification based on bispectral satellite imagery 总被引：5，自引：0，他引：5
A bispectral cloud classification method based on man-computer interactive way, i.e. a unit feature space clasification method (UFSCM), has been presented in this paper. Apart from land and water, six types of clouds including cumulonimbus, multilayer cloud system, thin / think cirrus, middle and low level clouds are recognized. The method has been tested by using more than two hundred samples, with total accuracy reaching 87.1%. 相似文献
13.
STUDIES OF THE VERTICAL STRUCTURE MODEL AND THE MICROWAVE ATTENUATION OF CLOUDS AND PRECIPITATION OVER TROPICAL OCEAN AREA* 下载免费PDF全文
下载免费PDF全文 Using radiosonde data and other related observations in the TOGA-COARE IOP(from November 1,1992 to February 28,1993),the microwave attenuation of non-precipitating clouds is investigated based on microwave radiative transfer model(MRTM) at the specific frequencies of 6.8,10.65,13.9,19.35,22.235,37.0,85.5 and 90.0 GHz.Besides,utilizing the data of the airborne radar and radiometer at 13.8 GHz in the IOP(Intensive Observation Period),vertical structure models for different types of precipitating clouds are obtained,and also the microwave attenuation of precipitating cloud is studied.Some statistical characteristics of 13.8 GHz microwave path integrated attenuation for stratiform and convective precipitating clouds are presented.The results given here are valuable for the spaceborne microwave remote sensing of precipitation,and the cloud and precipitation attenuation corrections in the spaceborne microwave remote sensing of earth surface over tropical ocean area. 相似文献
14.
云液态水柱含量是一个重要的气象学和云雾物理参数.对于云液水柱含量测量已发展了多种技术,但由于云在时空上变化很大,目前地基、飞机以及卫星测量的全部资料,都不能满足数值天气预报、人工增雨及气候变化研究等方面的工作需要.作者提出一种测云水的新方法,即从卫星-地面的微波衰减来确定云水(斜)柱量,并研究了此方法中的测量通道选择及测量方式问题,进行了初步的误差分析研究.结果表明,此方法在现有技术条件下可行,云水的测量精度不难达到20%～30%的水平.与卫星被动微波遥感结合起来,可获得精度更高的云水全球分布资料. 相似文献
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Summary Crystal size and optical depth of optically thin cirrus clouds and contrails over the North Sea and Adriatic Sea on the 18th of October 1989 are retrieved by comparison of NOAA AVHRR/2 brightness temperatures of channel 4 (9.97 µm–11.56 µm) and channel 5 (11.075 µm–12.76 µm) with one dimensional radiative transfer calculations. Measured brightness temperatures in all three infrared channels and their differences show higher values for contrails than for cirrus. The radiative properties of young contrails are consistent only, if smaller crystal size than those given for natural cirrus are adopted for the calculations. However, there is a continuous transition in radiative parameters between clouds classified as natural cirrus or contrails. For the test areas ice clouds are classified with respect to optical depth and mean crystal size. Finally infrared fluxes and heating rates in the spectral range 4 µm–40 µm are calculated for an atmosphere with a 500 m thick contrail or cirrus uncinus. At given ice content a far stronger atmospheric warming is found for a contrail with relatively small ice crystals: up to 80 K/day at cloud base for an ice content of 0.05 gm–3 compared to 10 K/day for a cirrus uncinus with large crystals.With 11 Figures 相似文献
17.
In this paper, characterization of cirrus clouds are made by using data from ground based polarization lidar and radiosonde measurements over Chung-Li (24.58°N, 121.10°E), Taiwan for a period of 1999–2006. During this period, the occurrence of cirrus clouds is about 37% of the total measurement nights over the lidar site. Analysis of the measurement gives the statistical characteristics about the macrophysical properties such as occurrence height, ambient temperature, and its geometrical thickness while the microphysical properties are interpreted in terms of extinction coefficient, optical depth, effective lidar ratio and depolarization ratio. The effective lidar ratio has been retrieved by using the simulation technique of backscattered lidar signals. The effect of multiple scattering has been taken into the account by a model calculation. Summer (Jun–Aug) shows the maximum appearances of cirrus due to its formation mechanism. It is shown that tropopause cirrus clouds may occur with a probability of about 24%. These clouds are usually optically thin and having laminar in structure with some cases resembling the characteristics similar to that of polar stratospheric clouds (PSCs). The radiative properties of the cirrus clouds are also discussed in detail by the empirical equations with results show a positive feedback on any climate change. 相似文献
18.
L. Stefanutti A. R. MacKenzie V. Santacesaria A. Adriani Stefano Balestri S. Borrmann V. Khattatov P. Mazzinghi V. Mitev V. Rudakov C. Schiller G. Toci C. M. Volk V. Yushkov H. Flentje C. Kiemle G. Redaelli K. S. Carslaw K. Noone Th. Peter 《Journal of Atmospheric Chemistry》2004,48(1):1-33
The APE-THESEO campaign was held from 15 February to 15 March 1999 from the Seychelles in the western Indian Ocean. APE-THESEO stands for Airborne Platform for Earth observation — (contribution to) the Third European Stratospheric Experiment on Ozone. The campaign aimed to study processes controlling the low water content of the stratosphere, including the mechanisms of cloud formation in the tropical tropopause region, and transport processes, studied using measurements of long-lived trace gases and ozone.Two aircraft were used: the high-altitude research aircraft, M-55 Geophysica, which can fly up to 21 km, and the Falcon of the Deutsches Zentrum für Luft- und Raumfahrt, a tropospheric aircraft. Seven flights were performed, including the first simultaneous in situ and remote sensing of sub-visible cirrus clouds, the first interception of sub-visible cirrus using in-flight guidance from a path-finding aircraft, and guided descent of a high-altitude research aircraft into the anvil cloud at the top of a tropical cyclone. In this paper we describe the payload used, the objectives for each flight, and the meteorological conditions encountered. First results show that a new type of cloud, which we have dubbed ultra-thin tropical tropopause cloud (UTTC), has been observed frequently, and observed to cover areas of 105 km2. The frequent coincidence of the tropopause and hygropause implies that the western Indian Ocean played an important role in the dehydration of the lower tropical stratosphere during the season of the mission. UTTCs, sub-visible cirrus, and visible cirrus, have all been implicated in the observed dehydration. Tracer measurements indicate little mixing of stratospheric air into the upper tropical troposphere. 相似文献
19.
青藏高原、东亚季风区、西北太平洋地区云系结构及相联加热机制的对比分析 总被引：1，自引：0，他引：1
应用7年(2006年5月18日—2013年5月18日)的CloudSat卫星观测资料,对比分析了青藏高原、东亚季风区、西北太平洋地区云发生频率的特征,并利用欧洲中心再分析资料,计算了三个地区的视热源、视水汽汇Q1、Q2,分析探讨了三个地区与云发生频率相联系的加热机制。结果表明:青藏高原、东亚季风区、西北太平洋地区云的发生频率分别为35%、22%、27%,其中:青藏高原和东亚季风区的低云频率最大,中云次之;西北太平洋地区的高云和低云的频率大,分别为19%和16%。具体云型来看,青藏高原多高层云、雨层云;东亚季风区多高层云和卷云,夏季深对流云频率增大明显;西北太平洋地区多卷云、深对流云和高层云。三个地区视水汽汇Q2的垂直分布特征及季节变化与云发生频率对应较好,青藏高原的低云(雨层云)、中云(高层云)形成过程中,凝结释放潜热,加热大气;东亚季风区低云(深对流云)、中云(高层云)对加热大气贡献大;西北太平洋地区大气的主要加热机制是深对流云形成过程中凝结释放潜热以及湿静能涡旋垂直输送。 相似文献
20.
Summary Precipitation, cloud water amount and phase, and water vapor amount are very important parameters in understanding the development of typhoons and their influence on the atmosphere and ocean. In this paper, we investigate the atmospheric water balance of Typhoon Nina, which formed near (5°N, 160°E) on November 18, 1987 and moved northwestward during its development. Water vapor path, liquid water path, ice index, and precipitation amount are determined in the vicinity of the typhoon using data from the SSM/I (Special Sensor Microwave/Imager). The water balance of the, typhoon cloud is then examined during its different development stages. An ice index is derived using SSM/I data that is used to investigate the overall ratio of ice/liquid water change of the typhoon during its development. By comparing the ice/water ratio of different mesoscale convective cells in the typhoon, attempts are made to interpret the different cloud structures and development stages of individual mesoscale cloud cells relative to their position from the typhoon center.It is found that the atmospheric water budget in the typhoon is mainly balanced by horizontal transport of water vapor into the region, evaporation from the ocean and precipitation. Of the two source terms, horizontal transport plays the major role with a contribution of more than 65% in all storm stages for 1° radial area or larger. In addition, the horizontal transport of water vapor seems to occur through several bands instead of uniform convergence. Mesoscale convective cells, which may consist of several cumulonimbus clouds in each, develop in the bands, with convectively more active cells occurring upwind and the dissipating one downwind. It it also found that the maximum latent heat release precedes the maximum storm intensity.With 15 Figures 相似文献