A database containing sub-seasonal to seasonal forecasts from 11 operational 30 centres is available to the research community and will help advance our understanding of 31 the sub-seasonal to seasonal time range.Abstract 51 52Demands are growing rapidly in the operational prediction and applications communities for 53 forecasts that fill the gap between medium-range weather and long-range or seasonal 54

The fine structure of super clusters was analyzed using the 3-hourly Geostationary Meteorological Satellite (GMS) Infrared (IR) data. A super cluster is defined as an ensemble of cloud clusters having different life stages with an observed horizontal scale of several thousand kilometers found near the equator during the active phase of intraseasonal variations (ISVs). Super clusters move eastward with a phase speed of about 10-15ms-1. GMS IR data reveal that the life time of each cloud cluster within a super cluster is about 1-2 days and its phase propagation is westward along the equator. Although each cloud cluster moves westward, a super cluster moves eastward due to the successive formation of a new cloud cluster east of the mature-stage cloud cluster. The above results suggest the existence of a hierarchy of convective activity in the tropical atmosphere.During the onset phase of the 1986/87 ENSO event in November 1986, an eastward moving super cluster was observed over the western Pacific to the dateline.

Rainfall is a fundamental process within the Earth's hydrological cycle because it represents a principal forcing term in surface water budgets, while its energetics corollary, latent heating, is the principal source of atmospheric diabatic heating well into the middle latitudes. Latent heat production itself is a consequence of phase changes between the vapor, liquid, and frozen states of water. The properties of the vertical distribution of latent heat release modulate large-scale meridional and zonal circulations within the Tropics, as well as modify the energetic efficiencies of midlatitude weather systems. This paper highlights the retrieval of latent heating from satellite measurements generated by the Tropical Rainfall Measuring Mission (TRMM) satellite observatory, which was launched in November 1997 as a joint American–Japanese space endeavor. Since then, TRMM measurements have been providing credible four-dimensional accounts of rainfall over the global Tropics and subtropics, information that can be used to estimate the space–time structure of latent heating across the Earth's low latitudes. A set of algorithm methodologies for estimating latent heating based on precipitation-rate profile retrievals obtained from TRMM measurements has been under continuous development since the advent of the mission s research program. These algorithms are briefly described, followed by a discussion of the latent heating products that they generate. The paper then provides an overview of how TRMM-derived latent heating information is currently being used in conjunction with global weather and climate models, concluding with remarks intended to stimulate further research on latent heating retrieval from satellites.

Based on FGGE Level IIIb data, the structural features of 40-50 day oscillations over ann extensive region (30*S-30*N, 30*E-150*W) during the 1979 summer are detailed.The analysis confirms earlier investigations that these low frequency modes are primarily associated with the zonal wind oscillations.These 40-50 day perturbations propagate northward and eastward, which is most clearly defined over the monsoon region north of the equator from 60* to 150*E. The monsoon region is characterized by prominent spectral peaks in the 850mb meridional winds with periods shorter than 10 days, probably reflecting the activities of monsoon disturbances.However, the local Hadley circulation, as defined by averaging the meridional component of the wind between 60* and 150*E, exhibits a distinct spectral peak in the period range of 40-50 days.Similarly, the square of the meridional winds, which is a measure of synoptic-scale disturbance activity, also changes with a period of 40-50 days. These features, which are similar to the group velocity phenomena, are pronounced only over the central monsoon region (10*-20*N, 60*-150*E). The low frequency modes propagate northward and become most intensified near 10*-20*N through mutual interaction between synoptic-scale disturbances, the local Hadley circulation, and the tonal mean flows over the monsoon region.At the equator, the 40-50 day zonal wind pertubations propagate systematically eastward (500km/day) and upward (0.7km/day). In the equatorial region, the low frequency oscillations owe their existence to a lateral geopotential wave-energy flux from the monsoon region, which represents the major energy source for 40-50 day perturbations via the conversion from potential to kinetic enegy.Compared to the equator, the phase propagation of zonal wind perturbations along 15*N, although moving eastward, is not as systematic.At this latitude, zonal wind perturbations are pronounced in the lower troposphere over the monsoon region, and also in the upper troposphere over the western Pacific. As an integral part of E-W interaction between these two regimes, there occurs downward progression of westerly (or easterly) perturbations over to the Arabian Sea region.The downward phase of westerly (easterly) modes corresponds to the commencement of "active" ("break") monsoons over South and Southeast Asia.

The purpose of the International Global Precipitation Measurement (GPM) Program is to develop a next-generation space-based measuring system which can fulfill the requirements for frequent, global, and accurate precipitation measurements. The associated GPM Mission is being developed as an international collaboration of space agencies, weather and hydrometeorological forecast services, research institutions, and individual scientists. The design and development of the GPM Mission is an outgrowth of valuable knowledge and published findings enabled by the Tropical Rainfall Measurement Mission (TRMM). From the TRMM experience, it was recognized that the GPM Mission must consist of a mixed nonsunsynchronous and sunsynchronous orbiting satellite constellation in order to have the capability to provide physically based retrievals on a global basis, with ~3-h sampling assured at any given Earth coordinate ~90% of the time. The heart of the GPM constellation is the Core satellite, under joint development by NASA and the Japan Aerospace Exploration Agency (JAXA), which will carry a dual frequency Ku/Kaband precipitation radar (PR) and a high-resolution, multichannel passive microwave (PMW) rain radiometer. The core is required to serve as the calibration reference system and the fundamental microphysics probe to enable an integrated measuring system made up of additional constellationsupport satellites, each carrying at a minimum some type of PMW radiometer. In this article the background, planning, design, and implementation of the GPM is described.