Shuichiro Katagiri

Radiative and microphysical properties of cirrus cloud inferred from infrared measurements made by the moderate resolution imaging spectroradiometer (MODIS). Part I: Retrieval method

AbstractAn optimal estimation–based algorithm is developed to infer the global-scale distribution of cirrus cloud radiative and microphysical properties from the measurements made by the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) at three infrared (IR) window bands centered at 8.5, 11, and 12 μm. Cloud-top and underlying surface temperatures, as a priori information, are obtained from the MODIS operational products. A fast-forward model based on semianalytical equations for the brightness temperature is used. The modeling errors in brightness temperature are mainly from the uncertainties in model parameters including surface emissivity, precipitable water, and cloud-base temperature. The total measurement–model errors are well correlated for the three bands, which are considered in the retrieval. The most important factors for the accurate retrieval of cloud optical thickness and the effective particle radius are cloud-top and surface temperatures, whereas model parameter uncertainties con...

Long term analysis of cirrus clouds' effects on shortwave and longwave radiation derived from data acquired by ground-based and satellite-borne observations

Radiative forcing caused by cirrus clouds and aerosols were computed using the data obtained with lidar installed at the Fukue Island observatory. The MTSAT data were used to discriminate the existence of cirrus clouds. Small fluctuation of cirrus cloud radiative forcing was estimated, and the effects caused by aerosols were also computed around Fukue Island from the end of 2005 to 2010.

Cirrus cloud radiative forcing at the top of atmosphere using the nighttime global distribution with the microphysical parameters derived from AVHRR

The radiative effect of cirrus clouds is particularly ambiguous in the climate research. We calculated the global cirrus cloud radiative forcing (CRFci) distributions at the top of the atmosphere (TOA) using the cloud microphysical parameters of effective radius (Re), optical thickness (COT) and the cloud top temperature (CTT) derived from AVHRR nighttime data. The results indicate that cirrus clouds warm the atmosphere, and in particular produce a large warming effect in the tropics. We also computed the dependence of radiative forcing on the effective radius of cloud particles, the optical thickness of the cloud, and the cloud-top temperature (CTT) and determined that cooling effects occur with clouds when their optical thickness is greater than 4.0∼4.5 with a cloud top temperature of 220K and 2.5∼3.0 with a cloud top temperature of 235K. Cloud radiative forcing in April 1987 (El Nino year) and April 1990 (neutral year) were computed, and found that a larger amount of cirrus clouds appeared in the tropics off Peru in 1987 than in 1990. But the globally averaged net cloud radiative forcing was smaller by 0.55W/m2 in 1987 than in 1990. Consequently, the temperature distribution of the oceans has a global effect on atmospheric warming and cooling.

Observed radiative effects caused by yellow dust aerosol at Sendai

A yellow dust event with moderate strength was observed on 9 April 2012 at Sendai in North part of Japan. Backward trajectory calculations with NOAA HYSPLIT showed the complex flow of aerosols into the North Japan. The sharp edge of this dust cloud was recognized by the data taken at several observatories, and the dust cloud conducted by low pressure system had heterogeneous structure, therefore very complicated interaction among aerosols may occur. Mie scattering lidar data was used to reproduce the radiative effect caused by this yellow dust event at Sendai with radiative transfer model. The results estimated every 15 minutes of radiative forcing at the top of the atmosphere and at the bottom of the atmosphere. The results show the slight warming effects < 6.5 W/m2 during night time both at the top and the bottom of the atmosphere, and during day time the large cooling effects < 150 W/m2 at the bottom and < 60W/m2 at the top of the atmosphere.

Cloud properties observed by Global Imager (GLI)

The data analyses of the ADEOS-II (Midori-II) GLI data have started. The optical and microphysical properties of warm water and cold ice clouds were retrieved by use of originally developed GLI data analysis algorithms. On the one-month mean results of warm water cloud in April 2003, very thick cloud optical thickness appeared in the east coast of the North America, the East Europe, and the South-East Asia. The moderately optically thick area spread over the Atlantic Ocean and West to Middle Pacific oceans. The effective radius was smaller on the continents and coastal area than ocean area. Especially, the South-East Asia to the middle pacific area where often covered with aerosols coming from continent in April, is the region of the smaller cloud effective particles. For the cirrus clouds, the smaller effective radii and larger effective radii can be obtained in low-to-mid and mid-to-high latitude area, respectively. Very low cloud top temperatures around 210K were often observed in the tropics. Warmer cloud top temperatures ranging from 220 to 240K were widely seen both over continental and oceanic area in mid-to-high latitude area.

Power laws for the backscattering matrices in the case of lidar sensing of cirrus clouds

The data bank for the backscattering matrixes of cirrus clouds that was calculated earlier by the authors and was available in the internet for free access has been replaced in the case of randomly oriented crystals by simple analytic equations. Four microphysical ratios conventionally measured by lidars have been calculated for different shapes and the effective size of the crystals. These values could be used for retrieving shapes of the crystals in cirrus clouds.

Application of a precipitating cloud classification method to radar observations in Thailand

The classification of precipitating cloud systems over Thailand was attempted by using cloud radar reflectivity data separated into convective and stratiform clouds based on a reflectivity threshold. A statistical technique is applied to examining the development of small-scale variability of radar reflectivity over the mesoscale storm. The convective cloud generally brings about higher rain rate than the stratiform cloud. After applying the classification method, rainfall estimation by radar was improved by using specific parameters for each rain type. Moreover, the classified results show consistency with TRMM 2A25 product.

Categorizing precipitating clouds by using Radar and Geostationary satellite

The classification of precipitating cloud systems over Thailand was attempted by using radar reflectivity and Multifunctional Transport Satellites (MTSAT) infrared brightness temperature (TBB) data. The proposed method can classify the convective rain (CR) area, stratiform rain (SR) area and non-precipitation area such as cumulus and cirrus cloud by applying an integrating analysis of rain gauge, ground-based radar and geostationary satellite data. Since the present study focuses on precipitation, the classified results of precipitation area are used to estimate quantitative precipitation amount. To merge different rainfall products, the bias between the products should be removed. The bias correction method is used to estimate spatially varying multiplicative biases in hourly radar and satellite rainfall using a gauge and radar rainfall product, respectively. An extreme rain event was selected to obtain the multiplicative bias correction and to merge data set. Correlation coefficient (CC), root mean square error (RMSE) and mean bias are used to evaluate the performance of bias correction method. The combined radar-MTSAT method is a simple and useful method. This method has been successfully applied to merge radar and gauge rainfall for hydrological purpose.