Impact of Physical Initialization on the Navy Operational Global AtmosphericPrediction System (NOGAPS)

摘要

A goal of the many numerical weather prediction centers is to improve thedefinition of the initial state and forecasts within the tropics. The difficulty of this problem and its resolution should not be understated. The tropics comprise about 50 percent of the surface area of the Earth and are very poorly sampled with respect to the middle latitude land areas. This is partially due to the fact that most of the tropics is ocean and the island stations are often far apart leaving wide gaps in the tropics with poor sampling in the vertical. Therefore, every piece of data is uniquely important due to its elevated level of importance in the analysis system. Physical or diabatic initialization is an attempt to improve the analysis of the basic state variables by using nonconventional data like rainrates, outgoing longwave radiation or condensation heating rates derived from rainrates. Davidson and Puri (1992), as well as Mathur (1995) and Kasahara et al. (1994) among others, have examined techniques ranging from the use of satellite radiometric imagery data to Newtonian relaxation in order to improve the divergent circulation, the description of the moisture variable and to reduce model 'spin up' of the hydrologic cycle. Krishnamurti et al. (1994) examined a month of continuous physical initialization cases and found a decidedly positive impact on the short-range forecast of convective precipitation.