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.
Downward longwave radiation is a key process to understand the climate change, energy budget, and water cycle at the
earth’s surface. Cloud is a dominant factor to determine the intensity of longwave radiation. It is widely known that
cloud cover and cloud base height (CBH) have strong effects on the downward longwave radiation, however there are
not so many studies regarding the quantitative evaluation of relationship between cloud properties and downward
longwave radiation.
The intent of the present study is to quantify the impact of cloud property on the downward longwave irradiance (DLI).
We used the data obtained with CGR-4 pyrgeometer at Tateno, Japan for the period from January 2002 to December
2011. Cloud radiative contribution fraction (CRC) is evaluated with a ratio of the difference of DLI between observation
under cloudy sky without precipitation and calculation assumed clear-sky condition to the observed DLI. The difference
between calculation and observation is -4.60±3.00 W/m2, and the calculation method reproduced to observation. Cloud is classified into three types by CBH, low (CBH<2000 m), middle (2000≥CBH<5000 m), and high (CBH≥5000 m).
In the results, CRC is almost proportional and inverse proportional to cloud cover (CC) and CBH in the average,
respectively. However, CRC for low cloud shows proportion to CBH because existence of low altitude cloud is related to
large precipitable water (PW).
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.
Low clouds are widespread over the North Pacific Ocean during summer. Past ship observations, which were carried out
in the western region of the North Pacific Ocean, suggested that low clouds (stratus and fog) are likely to occur when sea
surface temperature (SST) is lower than surface air temperature (SAT). In this study, we investigated the SST-SAT
relationship and microphysical properties of low clouds for the first step of understanding the mechanism of cloud
occurrence, maintenance and disappearance by using MODIS satellite observations, JAMSTEC ship observations and
MERRA reanalysis data. We divided the North Pacific into four regions according to meteorological condition and made
basic statistical analysis about cloud properties in each region by using monthly mean data for July 2011. The statistical
analysis indicates that in the central region of the North Pacific where SST-SAT value is negative and the difference is
the largest, cloud effective particle radius (re) is larger than those in other regions. We also used ship observation data and simultaneous satellite observation data to examine the relationship between SST-SAT and cloud microphysical properties in detail. This analysis indicates that re in the positive SST-SAT area is larger than that in the negative SSTSAT area. This feature is opposite to the monthly mean results. It suggests that other factors such as humidity and aerosols as well as SST-SAT have to be taken into account, although the SST-SAT relationship can be one of the
important factors determining cloud microphysical properties in the summer North Pacific region.
Effects of cloud horizontal inhomogeneity on the shortwave reflection are investigated from the viewpoint of cloud optical thickness retrieval for overcast boundary layer clouds. Monte Carlo radiative transfer model is employed to simulate bidirectional reflection functions in 1-km spatial resolution, for inhomogeneous cloud field that is generated by two-dimensional bounded cascade model. The independent pixel approximation (IPA) biases in mean (M) and standard deviation (S) of logarithm of retrieved optical thickness are defined, where S denotes cloud inhomogeneity parameter. The biases describe modification of the frequency distribution of optical thickness from true one due to effects of horizontal radiation transport. It is ascertained that observation in off-nadir view with oblique sun is inappropriate for optical remote sensing of clouds since the horizontal inhomogeneity produces large uncertainty. It is found that the radiation field substantially looks smoother than IPA with overhead sun, while it looks rough with oblique sun, especially in forward scattering view. The regression formulae of the IPA biases are presented for geometrically rough cloud field, and the parameterizations are easily applicable to first order correction of the optical thickness retrieval.
Cloud microphysical parameters such as optical thickness, effective particle radius, and liquid water path are obtained by measuring reflected or emitted radiation at various wavelengths from visible to microwave spectral region. Individual methods have both advantage and disadvantage since the cloud radiative properties are dependent on the relationship between particle size distribution and wavelength of radiation. Therefore comparison of retrieved parameters between different remote sensing measurements is important. On the other hand, the combination of various types of sensor is quite effective to the retrieval of cloud properties. In this study, some issues on the comparison between satellite remote sensing and groundbased or aircraft observations are discussed and some ideas such as statistical method are presented.
The polarization corrected temperature (PCT) derived from SSM/I 85 GHz data is used for the retrieval of rainfall rate over South China in the summer season. The 85 GHz PCT observed from space is strongly dependent on the emission and scattering by cloud and rain droplet particles. Hourly rain gauge measurement data were used to relate PCT with surface rainfall rate. Since the rainfall phenomena have large variabilities in time and space, a direct comparison between rain gauge measurement and satellite measurement is not adequate. On the other hand the rainfall rate distribution in a wide area does not change even if the measurement time is slightly different. Therefore the rainfall rate distribution measured with rain gauge and PCT change distribution were compared and a relationship between them is constructed. By applying it to SSM/I data, rainfall properties over the South China during periods from June to August of 1991-1995 were investigated.
Several methods are proposed in this study to retrieve some cloud physical parameters from ground-based simultaneous observations with a microwave radiometer and other instruments. When cloud is thin, liquid water path and columnar water vapor amount can be retrieved to be consistent with measured intensities of two frequencies around 20 GHz and around 30 GHz under the assumption of homogeneous cloud temperature. In this retrieval procedure, cloud temperature, which affects the calculated value of liquid water path seriously, is given form measurement with an IR radiative thermometer. The effective radius of cloud particles is also derived from comparing the measured downward solar flux on the ground surface to calculated one. For the thick cloud, which is expected that the temperature difference between top and bottom of cloud is large, cloud top temperature is also retrieved from narrow view angle measurements of transmitted radiance of solar radiation at two wavelengths in addition to microwave measurements. The liquid water path is deduced from the comparison of measured radiances at the two wavelengths to the calculated values, thus the appropriate cloud top temperature can be retrieved to be consistent with the measured microwave intensity at two frequencies. Practices suggested that the observation with a microwave radiometer and a pyrnometer enables to derive the detail of cloud structure.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.