The subtropical global plume in the Pacific Exploratory Mission-Tropics A (PEM-Tropics A), PEM-Tropics B, and the Global Atmospheric Sampling Program (GASP): How tropical emissions affect the remote Pacific

[1] An extended southern subtropical plume of CO meanders>15,000 km around the world, gradually spreading around 20 S. This southern pollution plume is most noticeable in the burning season, southern spring; a similar subtropical plume appears in the northern spring. We use tracer maps to guide the use of trajectories to trace observations of the plume to their origins. The MM5 mesoscale model provides high-resolution, near-global synoptic reconstructions of the weather. Two situations are analyzed: NASA’s airborne Pacific Exploratory Mission-Tropics A (PEM-Tropics A) period, September–October 1996 and the PEM-Tropics B period, March–April 1999. Similar features are noted for a much earlier mission in 1977, which apparently captured the first, but never-recognized, samples of the global pollution of the Southern Hemisphere. For PEM-Tropics A, near-source pieces of the plume are clearly seen in the Total Ozone Mapping Spectrometer (TOMS) absorbing aerosol product and are well simulated. Downwind, the aircraft sampling of several strands deriving from a single plume seems representative and well simulated. A general mechanism of the plume emerges: The southern plume arises in surface accumulation regions in Africa and Sout

The role of the equivalent blackbody temperature in the study of Atlantic Ocean tropical cyclones

Satellite measured equivalent blackbody temperatures of Atlantic Ocean tropical cyclones are used to investigate their role in describing the convection and cloud patterns of the storms and in predicting wind intensity. The high temporal resolution of the equivalent blackbody temperature measurements afforded with the geosynchronous satellite provided sequential quantitative measurements of the tropical cyclone which reveal a diurnal pattern of convection at the inner core during the early developmental stage; a diurnal pattern of cloudiness in the storm's outer circulation throughout the life cycle; a semidiurnal pattern of cloudiness in the environmental atmosphere surrounding the storms during the weak storm stage; an outward modulating atmospheric wave originating at the inner core; and long term convective bursts at the inner core prior to wind intensification

Predicting tropical cyclone intensity using satellite measured equivalent blackbody temperatures of cloud tops

A regression technique was developed to forecast 24 hour changes of the maximum winds for weak (maximum winds less than or equal to 65 Kt) and strong (maximum winds greater than 65 Kt) tropical cyclones by utilizing satellite measured equivalent blackbody temperatures around the storm alone and together with the changes in maximum winds during the preceding 24 hours and the current maximum winds. Independent testing of these regression equations shows that the mean errors made by the equations are lower than the errors in forecasts made by the peristence techniques

Studies of satellite support to weather modification in the western US region

The applications of meteorological satellite data to both summer and winter weather modification programs are addressed. Appraisals of the capability of satellites to assess seedability, to provide real-time operational support, and to assist in the post-experiment analysis of a seeding experiment led to the incorporation of satellite observing systems as a major component in the Bureau of Reclamations weather modification activities. Satellite observations are an integral part of the South Park Area cumulus experiment (SPACE) which aims to formulate a quantitative hypothesis for enhancing precipitation from orographically induced summertime mesoscale convective systems (orogenic mesoscale systems). Progress is reported in using satellite observations to assist in classifying the important mesoscale systems, and in defining their frequency and coverage, and potential area of effect. Satellite studies of severe storms are also covered

Remote sensing of precipitable water over the oceans from Nimbus-7 microwave measurements

Global maps of precipitable water over derived from scanning multichannel microwave radiometer (SMMR) data reveal salient features associated with ocean currents and the large scale general circulation in the atmosphere. Nimbus-7 SMMR brightness temperature measurements in the 21 and 18 GHz channels are used to sense the precipitable water in the atmospheric over oceans. The difference in the brightness temperature (T sub 21 -T sub 18), both in the horizontal and vertical polarization, is found to be essentially a function of the precipitable water in the atmosphere. An equation, based on the physical consideration of the radiative transfer in the microwave region, is developed to relate the precipitable water to (T sub 21 - T sub 18). It shows that the signal (T sub 21- T sub 18) does not suffer severely from the noise introduced by variations in the sea surface temperature, surface winds, and liquid water content in non rain clouds. The rms deviation between the estimated precipitable water from SMMR data and that given by the closely coincident ship radiosondes is about 0.25 g/ sq c

Tropical cyclone intensities from satellite microwave data

Radial profiles of mean 1000 mb to 250 mb temperature from the Nimbus 6 scanning microwave spectrometer (SCAMS) were constructed around eight intensifying tropical storms in the western Pacific. Seven storms showed distinct inward temperature gradients required for intensification; the eighth displayed no inward gradient and was decaying 24 hours later. The possibility that satellite data might be used to forecast tropical cyclone turning motion was investigated using estimates obtained from Nimbus 6 SCAMS data tapes of the mean 1000 mb to 250 mb temperature field around eleven tropical storms in 1975. Analysis of these data show that for turning storms, in all but one case, the turn was signaled 24 hours in advance by a significant temperature gradient perpendicular to the storm's path, at a distance of 9 deg to 13 deg in front of the storm. A thresholding technique was applied to the North Central U.S. during the summer to estimate precipitation frequency. excep

On the sensitivity of Sverdrup transport estimates to the specification of wind stress forcing in the Tropical Pacific

We use Sverdrup dynamics to estimate geostrophic transports between 20°N and 20°S in the Tropical Pacific Ocean averaged over the period 1979-1981. Three wind stress products are used to force the model. Results are compared to geostrophic transports computed along expendable bathythermograph transects in the Western, Central, and Eastern Pacific for the same period. Depending on the choice of wind stress, modeled transports may differ from the observations by a factor of 2 and, in some cases, flow is opposite to that observed. Possible limitations of the Sverdrup theory are discussed; however, we conclude that detailed and accurate simulation of the general circulation in the Tropical Pacific is limited more by the uncertainties in presently available estimates of the surface wind stresses than by deviations from Sverdrup balance. (Résumé d'auteur

The global monsoon system: research and forecast

The main objective of this workshop was to provide a forum for discussion between researchers and forecasters on the current status of monsoon forecasting and on priorities and opportunities for monsoon research. WMO hopes that through this series of quadrennial workshops, the following goals can be accomplished: (a) to update forecasters on the latest reseach findings and forecasting technology; (b) to update researchers on monsoon analysis and forecasting; (c) to identify basic and applied research priorities and opportunities; (d) to identify opportunities and priorities for acquiring observations; (e) to discuss the approach of a web-based training document in order to update forecasters on developments of direct relevance to monsoon forecasting

On the Tropical Atlantic SST warm bias in the Kiel Climate Model

Most of the current coupled general circulation models show a strong warm bias in the eastern Tropical Atlantic. In this paper, various sensitivity experiments with the Kiel Climate Model (KCM) are described. A largely reduced warm bias and an improved seasonal cycle in the eastern Tropical Atlantic are simulated in one particular version of KCM. By comparing the stable and well-tested standard version with the sensitivity experiments and the modified version, mechanisms contributing to the reduction of the eastern Atlantic warm bias are identified and compared to what has been proposed in literature. The error in the spring and early summer zonal winds associated with erroneous zonal precipitation seems to be the key mechanism, and large-scale coupled ocean-atmosphere feedbacks play an important role in reducing the warm bias. Improved winds in boreal spring cause the summer cooling in the eastern Tropical Atlantic (ETA) via shoaling of the thermocline and increased upwelling, and hence reduced sea surface temperature (SST). Reduced SSTs in the summer suppress convection and favor the development of low-level cloud cover in the ETA region. Subsurface ocean structure is shown to be improved, and potentially influences the development of the bias. The strong warm bias along the southeastern coastline is related to underestimation of low-level cloud cover and the associated overestimation of surface shortwave radiation in the same region. Therefore, in addition to the primarily wind forced response at the equator both changes in surface shortwave radiation and outgoing longwave radiation contribute significantly to reduction of the warm bias from summer to fall