Douglas J. Parker on Upper-Air Measurements Over West Africa
New Hot Paper Commentary, September 2010
Where do you see your research leading in the future?
The data have been quality controlled, and have been used to evaluate the impacts of the measurements on weather prediction models. This means that in principle we can evaluate some kind of economic value (in terms of improved weather prediction) for each observation.
Unfortunately this work has exposed, or perhaps confirmed, the fact that our weather prediction models have some fundamental deficiencies for the tropics, and that until these problems are rectified the benefit of observations to a weather forecast is lost rather quickly, over a day or so. We simply need to improve our prediction models through deeper scientific analysis using the radiosonde and other data.
The measurements are now being used to quantify the water cycle, and are being used to evaluate and test the water cycle in weather and climate models. Right now, climate predictions of rainfall for West Africa diverge, with some predicting a wetter future and others predicting a drier future. Our long-term goal is to understand and correct these models so that we can make predictions with narrower levels of uncertainty.
"Our upper-air measurements represent the best sampling of the atmosphere which has ever been achieved over an African region, and therefore they are in demand by many studies into meteorology, hydrology, oceanography, and climate."
Our data have been assimilated into the European Centre for Medium Range Weather Prediction (ECMWF) model, whose products are used by many people worldwide. The years 2006-07 have the best atmospheric analyses for West Africa, and the impact of our data will be felt in the quality of analyses for other parts of the world, including Europe.
More effort is needed in future to sustain the radiosonde network in West Africa. Although the reactivated stations are continuing to do well since the AMMA effort began in 2005, the four new stations which we established have not continued to operate after the cessation of funding from scientific research budgets.
These new stations were located in places of climatic importance, where the monsoon winds bring moisture into the continent, and their silence is disappointing. We would like to see greater international effort to sustain these stations with consumables in the coming years.
Do you foresee any social or political implications for your research?
Weather prediction has a direct impact on society, particularly in West Africa where agriculture, water resources, and health (e.g. prevalence of malaria) depend on rainfall. Good weather forecasts, particularly in relation to seasonal events such as the onset of monsoon rains, or breaks in the rains, would have a major benefit to the survival of many people.
Right now in West Africa, weather predictions are generally unreliable for lead times greater than a day or so. Improving prediction models relies on the datasets provided by AMMA, of which the upper-air radiosonde dataset is one of the most important, and there are already some examples of AMMA results leading to model improvements.
In conducting this program, we were shocked by the continual waste of good and costly measurements, through failing communications networks. As part of their responsibility for aviation security, West African meteorological agencies deploy radiosondes worth millions of Euros every year. Sometime 50% of these data are lost to the international weather prediction services, through chronic failures of communication. The financial costs of fixing these problems would be relatively low, but a major cooperative effort would be needed.
We found that many of the communications failures can be corrected by an international management system in which there is direct dialogue between data collectors and users. One deep problem appears to be that the African meteorological agencies do not value the computer-based weather forecasts which are sent to them by the international forecasting centers—and our research does confirm that these forecasts have significant errors.
In some sense, when radiosonde measurements are transmitted from the African agencies, the products of these which are returned—weather prediction products—are not valued. If better numerical weather forecasts are generated, and their products are better valued by African agencies, then the motivation to communicate measurements will improve.
In our paper we argued that international agencies need to establish a better plan for the region, in order to direct funding where needed and in order to address problems in a timely manner. In the AMMA research program, a large number of people were highly motivated to fix technical and operational problems on the network, but there is a risk that this impetus will be lost as the intensive AMMA observational periods have passed.
We need good upper-air measurements from this region if we are to understand its physics, monitor its climate, and evaluate its effects on global weather forecasts, and this will require a collective international effort.
Douglas J. Parker
Institute for Climate and Atmospheric Science
School of Earth and
Environment
University of Leeds
Leeds, UK
KEYWORDS: FIELD CAMPAIGN; MONSOON; JET, Upper-Air Measurements, West Africa.