Search Results

You are looking at 1 - 10 of 10 items for :

  • Boundary conditions x
  • Assimilation of Satellite Cloud and Precipitation Observations x
  • All content x
Clear All
Fuzhong Weng

radiances and those computed based on the NWP output of the atmospheric state. In the absence of cloud absorption and atmospheric scattering from precipitation an accurately parameterized radiative transfer model was used to assimilate satellite measurements into global NWP models for clear atmospheric conditions (e.g., Eyre 1989 ; Garand et al. 2001 ). However, in order to utilize the full capabilities of AMSU and other advanced instruments, which includes all weather conditions, an accurate

Full access
Ronald M. Errico, George Ohring, Fuzhong Weng, Peter Bauer, Brad Ferrier, Jean-François Mahfouf, and Joe Turk

(radars and lidars) providing information on the vertical distribution of clouds and precipitation. The recently launched CloudSat carries a cloud radar that measures vertical profiles of cloud water and ice and vertical cloud boundaries with a 250-m resolution. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite has a 2-wavelength lidar that measures ice and water extinction profiles, and cloud heights of optically thin clouds, with a vertical resolution of 30

Full access
Fuzhong Weng, Tong Zhu, and Banghua Yan

NOAA-18 satellites and the Advanced Microwave Scanning Radiometer for Earth Observing System (EOS; AMSR-E) on board the National Aeronautics and Space Administration (NASA) EOS Aqua satellite. To extend radiance assimilation to all-sky conditions, we have upgraded the assimilation system with fast radiative transfer models that include scattering and emission from clouds and precipitation. 2. Satellite microwave observations under cloudy conditions The passive microwave radiation can penetrate

Full access
Christopher W. O’Dell, Peter Bauer, and Ralf Bennartz

assumption that the cloud object has a minimum areal extent within the layer; this tends to make square or circular-shaped clouds, as opposed to more one-dimensional cloud objects. Figure 4 shows the cloud distribution of the sample profile of Fig. 2 for the 3D approach using MR cloud overlap. In this particular case, three separate cloud objects are present. The distribution scheme for precipitation is the same physical approach as in the IC scheme. Another issue is that the boundary conditions are

Full access
Ruiyue Chen, Fu-Lung Chang, Zhanqing Li, Ralph Ferraro, and Fuzhong Weng

1. Introduction It has long been recognized that clouds play a dominant role in the earth’s climate and its changes. Clouds strongly affect the energy balance and water cycle, two dominant processes in the climate system. Low-level boundary layer clouds have the most significant influence on cloud radiative forcing because of their areal extent and frequency ( Harrison et al. 1990 ; Hartmann et al. 1992 ). Radiation absorbed by boundary layer clouds also plays an important role in the

Full access
Ronald M. Errico, Peter Bauer, and Jean-François Mahfouf

I: Basic issues and heuristic examples. J. Atmos. Sci. , 53 , 1123 – 1142 . Zhu , Y. , and I. M. Navon , 1999 : Impact of parameter estimation on the performance of the FSU global spectral model using its full-physics adjoint. Mon. Wea. Rev. , 127 , 1497 – 1517 . Zou , X. , and Y-H. Kuo , 1996 : Rainfall assimilation through an optimal control of initial and boundary conditions in a limited-area mesoscale model. Mon. Wea. Rev. , 124 , 2859 – 2882 . Zou , X. , I. M

Full access
Graeme L. Stephens and Christian D. Kummerow

steps described that confound the specification of uncertainties of the approach. These include the following: (i) The radiative transfer approximations, including the lack of infrared scattering (e.g., Stephens 1980 ) and the simplicity of the atmospheric model (single layer) implicit to Eq. (2) and upon which this transport equation is defined. (ii) The specification of the forward-model parameters. For this problem, these include the lower boundary radiance I below and the “cloud

Full access
Peter M. Norris and Arlindo M. da Silva

generalization of Slingo (1987) . The core of this scheme is a quadratic variation of cloud fraction, f , with relative humidity, RH, above a critical value, RH 0 , approaching complete cloud cover at 100% RH: The tuned version used in the GEOS-4 sets RH 0 = 87%. For mid–high clouds (<750 hPa) RH 0 is increased with a positive Brunt–Väisälä frequency to account for reduced subgrid-scale variability under stable conditions. For low clouds (≥750 hPa) RH 0 is reduced to 77% over snow-free land to account

Full access
Philippe Lopez

independent of meteorological conditions, Ricard and Royer (1993) and Lohmann et al. (1999) allowed their respective PDF variance to be modulated by turbulence inside the planetary boundary layer. Tompkins (2002) added even more complexity in his scheme by including the effect of both turbulence and convective activity on his beta distribution through two additional prognostic equations for variance and skewness. In cloud-resolving models (CRMs) that have been used only for research purposes so far

Full access
Chinnawat Surussavadee and David H. Staelin

meteorological conditions. Section 5 summarizes the prospects for assimilation of millimeter-wave precipitation-sensitive radiances and retrievals into numerical models, and the conclusions to be drawn from these studies. 2. Approach a. Physical basis Most prior centimeter-wave precipitation observations from satellites have used dual-polarized window channels below 90 GHz viewed at large constant zenith angles that permit surface emissivity and temperature to be partially distinguished, thus permitting

Full access