Showing papers in "Weather in 2002"

Climate change 2001: The scientific basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change

Abstract: The earth’s climate system has demonstrably changed since the pre-industrial era, with some of these changes attributable to human activities. The consequences of climate change pose a serious challenge to policy-makers. Hence they need an objective source of information about climate change, its impacts and possible response options. Recognising this, the World Meteorological Organization (WMO) and the United Nations Environmental Programme jointly established the Intergovernmental Panel on Climate Change (IPCC) in 1988. The terms of reference of the IPCC include:

Radiative forcing of climate change

Abstract: Our current understanding of mechanisms that are, or may be, acting to cause climate change over the past century is briefly reviewed, with an emphasis on those due to human activity. The paper discusses the general level of confidence in these estimates and areas of remaining uncertainty. The effects of increases in the so-called well-mixed greenhouse gases, and in particular carbon dioxide, appear to be the dominant mechanism. However, there are considerable uncertainties in our estimates of many other forcing mechanisms; those associated with the so-called indirect aerosol forcing (whereby changes in aerosols can impact on cloud properties) may be the most serious, as its climatic effect may be of a similar size as, but opposite sign to, that due to carbon dioxide. The possible role of volcanic eruptions as a natural climate change mechanism is also highlighted.

Observed climate variability and change

Abstract: Chapter 2 emphasises change against a background of variability. The certainty of conclusions that can be drawn about climate from observations depends critically on the availability of accurate, complete and consistent series of observations. For many variables important in documenting, detecting, and attributing climate change, data are still not good enough for really firm conclusions to be reached. This especially applies to global trends in variables that have large regional variations, such as pre-

Birds, weather and climate

Abstract: While humans are subject to the effects of weather and climate, wild birds are much more sensitive to them than we are. Ornithologists have long recognised this, and related their observations of migrating birds and of vagrant species from other parts of the world to weather patterns. Conversely, early studies of meteorology were frequently based on studies of the effects of climate on wildlife. In the early days of the Royal Meteorological Society (RMS) much of its work was concerned with the study of phenology, which directly studies variations in climate through the timings of events in nature. More recently, meteorologists have mostly turned to other forms of observations, but many fascinating links between the two sciences remain. Indeed phenology today may offer a powerful tool for the detection of climate change. Equally, climate change presents a serious threat to the future of many bird species, as habitats and weather patterns may be liable to change very rapidly at a time when bird populations are already forced into small pockets of habitat by human development. To study the many links between birds, weather and climate a meeting of the RMS was convened in March 2002, including the biennial Margary lecture (traditionally dedicated to phenology since Margary himself was a phenologist) presented by Tim Sparks of the Centre for Ecology and Hydrology. In this paper the speakers from that meeting summarise their presentations on the effects of both weather and climate on the lives of birds. The effect of weather on bird migration (Norman Elkins)

The UK MST radar

Abstract: designed to measure detailed vertical profiles of winds, waves and turbulence on a continuous basis. The profiles generally extend from 2 to 20km in altitude, covering the free troposphere and lower strato- sphere, with occasional echoes also from the mesosphere between 70 and 90 km. The radar was built by the Rutherford Appleton Labora- tory under the scientific direction of Prof. Lance Thomas at Aberystwyth.

Back to basics: Measuring rainfall at sea: Part 1 – In situ sensors

Abstract: Rainfall is an important climatic variable. Extremes in rainfall accumulations over land - either floods or droughts - have major societal implications and are obvious. At sea, the effects on human activity are less evident, apart from the inconvenience to deck passengers on cruise liners! However, improved knowledge of the rainfall associated with weather systems approaching the UK from the Atlantic would be beneficial to weather forecasting, especially if assimilated into atmospheric models. There is an additional, more subtle, effect involving the ocean itself. At sea, the balance between precipitation and evaporation provides a critical feedback in climate change.

Projections of Future Climate Change

Abstract: Contents: Executive Summary 9.1 Introduction 9.2 Climate and Climate Change 9.3 Projections of Climate Change 9.4 General Summary Appendix 9.1: Tuning of a Simple Climate Model toAOGCM Results References

Recent climate of southern Greenland

Abstract: The polar regions are among the most interesting regarding the ongoing debate on global climate change because, due to several key climatic feedbacks, they are potentially extremely climatically sensitive. The best known is the ice± albedo feedback by which an initial perturbation (slight warming) melts some ice; this new, more extensive, darker, melt-water area absorbs more incoming sunlight, which accelerates the warming and melting of surrounding ice. Therefore, it is crucial to improve our understanding of current conditions and past history of the major ice sheets and sea-ice, and to model how they are likely to behave in future (e.g. in response to man-made global warming). This requires not only glaciological observations but also meteorological ones. Unfortunately, polar areas are noted for their dearth of observations.

A heavy winter monsoon rainfall episode influenced by easterly waves, a westerly trough, blocking and the ITCZ

Abstract: A recent five-day cricket Test Match between England and India held at Bangalore, India, from 19 to 23 December 2001 ended in a disappointing draw. England was leading with a very respectable first innings score when heavy rains started on Day 3 of the match and led to the cancellation of the game. Just before that, one of the authors of this paper had received an e-mail from a Bangalore colleague inquiring about the prospects of rain for the following days. This led to our interest in the examination of the synoptic situation during that period. Here we present a short account of our findings, which turned out to be quite intriguing. In this note we focus on the scenario that preceded the heavy rainfall episode over southeast India during the winter monsoon period in December 2001. A persistent anticyclonic circulation in the upper troposphere over east Africa, centred near 58N, 508E, contributed to the bifurcation of the strong westerlies near 208N into two streams. An intense and persistent blocking situation was present near 608E. One branch of the split flow in the westerlies moved equatorward in the Arabian Sea, resulting in a trough in the Northern Hemisphere and a ridge in the Southern Hemisphere, the latter residing over the Southern Hemisphere intertropical convergence zone (ITCZ) near 58S. This ridge± trough system provided a moist stream of south-westerly flow over the south-east coast of India where the frequent westward passage of easterly waves near 850mbar provides the setting for heavy rain. Another important feature within the easterly trades are the frequent wind surges. These surges move from east to west within the easterly trades at a speed of roughly 78 longitude per day. The average strength of the trades is around 12ms and the surges often carry a wind speed as high as 13 to 14ms. Commonly, convection and rain are found ahead of the surge, due to the convergence of mass and moisture. At the time of the heavy rain over Chennai (13.138N, 80.258E) we could clearly see the simultaneous arrival of an easterly wave and a trade surge over the south-east coast of India. Winter monsoon rains over the coast of south-east India usually occur during October, November and December, with heavier rains occurring in November and December. The large-scale flow field over the region exhibits a very strong vertical wind shear. At the surface levels, the flow is generally from the north-east (also called the north-east monsoon). As the winds veer with height, at the 850 mbar level the flow is more easterly. In the upper troposphere the winds generally tend to be more westerly (Krishnamurti et al. 1997a,b). The north-easterly monsoonal flow is very shallow, occupying only the lowest 2 km of the atmosphere.

Weather and pests

Abstract: Recent weather conditions have been mostly hot, humid and typical of mid-summer in Wisconsin. Corn has fared well in past weeks and nearly all fields except for a few in the northeastern and east central areas of the state met or exceeded the “knee-high by the 4th of July” mark. As of July 3, the statewide average corn height was 37 inches, slightly shorter than last year’s 38 inches, but above the 5-year average of 27 inches. Reports from Barron Co. and parts of the northwest and north central districts indicate fields are drought stressed and in urgent need of precipitation. The warming trend that is forecast to continue through the week ahead may cause the situation to worsen if no rain is received soon.

Springflow variability since 1858 in south Dorset

Abstract: Unlike many meteorological observation programmes, extensive hydrological monitoring in the UK only began in earnest during the 1960s. Although the UK is now blessed with a dense network of surface and groundwater monitoring sites, few long-term records are available. Only four river flow series held in the National River Flow Archive begin before 1900 and only one before the 1870s. Such records are exceptionally valuable, but are all, in some form, limited in their utility due to a lack of homogeneity. Although changes in flow-measurement techniques are often a factor, the increasingly important impact of man on hydrological processes is particularly influential and is discussed in detail elsewhere (Marsh 2001). Long-term records largely unaffected by man are of paramount hydrological value, particularly in relation to the detection of trends. The last decade has been marked by substantial climatological and hydrological variability (Green et al. 1996; Marsh 1996; Jones and Conway 1997). The notable severity of the autumn 2000 flooding thoughout the UK served to underline this erratic tendency. A measure of agreement between recent climatological and hydrological patterns and climate change scenarios (Arnell and Reynard 2000) has stimulated further research into trends in hydrological behaviour. Unfortunately, the average length of record for UK gauging sta-