For forecasting strong dust storms in the central and western areas of the Inner Mongolia Autonomous Region an objective discrimination approach has been developed. The 37 strong dust-storm events that occurred in this area during the last 40 years have been classified into four circulation patterns. Using the method suggested by Saaty (1996), a priority relationship matrix was set up and the discrimination function was then established. Depending on the function values, a judgement is then made about whether the real-time situation belongs to any of the four patterns and, if so, to which one. If there is a match, then this typical event can be used as a basis for forecasting a strong dust storm. The successful application of this approach is demonstrated using results from 1998 and 2000.

Owing to the decrease of stratospheric ozone during the southern spring (starting in September), the city of Punta Arenas (53.1°S, 70.9°W) and its surroundings are exposed to a high incidence of ultraviolet-B (UV-B) radiation during this period. Ozone denatures DNA, and prolonged exposure may cause skin carcinoma and cataracts. Consequently, there is great concern among the inhabitants of this region regarding the possible effects of long-term exposure to UV-B. In this work we apply and further develop a pilot study carried out in 1995 which looks at the simple operational method of forecasting ozone levels some 42 hours in advance. The method is based on the prediction of the 100 mb-temperature from ECMWF (European Centre for Medium-Range Weather Forecasts), which is well correlated with total column ozone levels. It allows the inhabitants of the Magallanes region to be alerted to potentially high incidences of UV-B radiation during the Austral spring.

A one-dimensional Kalman filter is proposed for the correction of maximum and minimum near surface (2 m) temperature forecasts obtained by a Numerical Weather Prediction model. In our study we used only one parameter (observed temperature), employing in this way scalar system and observation equations, and a limited time interval (7 days). As a result, our algorithm can be easily run on any PC with only minor technical support. The corresponding results are rather impressive, since the systematic error of our time series almost disappears, and they show the merit of post-processing even when only a simple method is applied.

This study compares the performance of different models used to assess the local wind near-surface conditions at an agricultural site in Scania, southern Sweden. The methods are: (a) the WASP model (Wind Analysis and Application Program), (b) separate linear regressions of the two wind vector components, (c) a regression model based on vector correlation, and (d) linear regression of scalar wind. Each method was tested with three different data sets over nine months: wind measurements from the nearby Sturup airport SYNOP station, 10 m surface wind and surface geostrophic wind produced by the operational Swedish Mesoscale Analysis system (Mesan). The wind climate estimations were compared with observed winds at the field site, with respect to mean wind speed, wind direction, wind speed frequency distribution and the relative frequency of winds above 6 m s−1. All models performed reasonably well with data from Sturup and Mesan surface wind, but gave less reliable results with the Mesan geostrophic data. The estimated frequency of winds above 6 m s−1 was in general lower than the observed frequency. Overall, best results were obtained with WASP in combination with measurements from Sturup.

In-situ methods for measuring upper tropospheric humidity are important for two reasons: (i) they can be used as accurate spot measurements with which to calibrate more extensive data from satellites and other sensors; (ii) they can provide high accuracy measurements from aircraft or balloon with which individual processes of transport, phase change or chemistry can be studied.

In either case the accuracy of the in-situ measurement is of paramount importance. This study compares the performance and accuracy of a resonance fluorescence type of sensor (the Fluorescence Water Vapour Sensor) with a standard frost-point hygrometer.

An intercomparison of these two hygrometers has confirmed a long-standing difference between these two types of sensors (the FWVS overestimates the water vapour volume mixing ratio by 10–20%, depending on pressure). Testing the FWVS experimentally in the laboratory, along with a modelling study of the sensor has revealed that a significant source of error is due to contamination of the FWVS source emission, and the subsequent underestimation of the oxygen absorption cross-section.

The Australian Bureau of Meteorology has been providing weather services for Australian Antarctic expeditions since the first expedition of 1947 and the forecasting services have been gradually evolving over the decades. However, with the advent of high bandwidth communications into Antarctica in the early 1990s there has been, for the first time, access to high-resolution satellite imagery, numerical model data and global observational datasets. Over the past seven years locally designed and developed forecast systems have matured and now provide the Antarctic forecaster with a comprehensive suite of systems to assist in the timely and accurate provision of aviation, marine and terrestrial forecasts. The ease with which these data may be manipulated, displayed and interpreted is expected to have a positive impact on the quality of forecasts provided to the Antarctic user.

A flood study of the Himalayan rivers has been attempted on the basis of gauge/discharge data from 27 sites on major tributaries of the Ganga between 1986 and 1999. This study has shown that the Ghaghra, Gandak, and Kosi are the most important tributaries of the Ganga and their flood waters should be harnessed for developmental purposes to save the Indo-Gangetic plains from the recurrence of yearly floods. It was also found that some of the sites on these rivers have recorded floods more than 100 to 150 times during the 14-year period.

Despite the potential importance for air pollution, the association between temperature inversions and vertical wind profiles has been paid scant attention. A preliminary statistical assessment is made, using message data from radiosonde soundings at a station in eastern England for the period 1976–1980, from the surface up to 700 mb. In spite of an expectation among many air pollution meteorologists that inversions and local wind maxima (or vertical wind shears) are ‘typically’ associated, no such typical association between inversions and significant wind levels was identified. This conclusion extended to nocturnal surface inversions and low level jets. This does not mean that there are not clear cases of association, but that either (a) the dataset does not discriminate the associations, and/or (b) the associations are not evident on a climatological, or statistical, basis.

A triple-nested regional weather prediction model was used to investigate the effects of the model horizontal resolution and orography on southwest monsoon precipitation over India. Numerical experiments with different resolution topography and different horizontal resolution model domains were conducted. Simulation results indicate that both the distribution and intensity of simulated southwest monsoon precipitation over India is highly sensitive to model horizontal resolution and topography. The model with a finer resolution is able to predict mesoscale organization of rainfall over the land mass. Rainfall predicted over the coarse domain is much less than that observed owing to its unrealistic representation of orographic effects and mesoscale forcings. Simulated wind speed, surface pressure, and latent and sensible heat flux distributions are also sensitive to the model resolution. Larger values and more detailed structure of the distribution of the wind speed and latent and sensible heat fluxes are simulated in the finer domains.

An operational system for diagnosing probability of convective development and structure from NWP model outputs over the British Isles has been developed in the Met Office. The system originated as a research and development project and so for historical reasons is now known as the Convection Diagnosis Project (CDP). The system takes account of expected model errors in temperature and humidity and allows for forcing from sub-grid scale mechanisms on a 1-km scale that are important for mid-latitude convection. A NWP convection scheme is used to determine grid-mean parameters from a range of forcings according to probability of occurrence. The grid-mean values are then used in a simple and variable object-oriented life-cycle model of a convective cloud to diagnose shower structure and expected movement. Using the life-cycle model, a range of probabilistic forecast outputs are produced four times a day from T+6 to T+36 hours ahead for individual grid squares and for larger pre-defined regions. Case studies and rigorous objective verification, making use of an automatic method for identifying convective cloud from radar and satellite data, have shown that the CDP outputs complement the standard NWP outputs and can provide additional useful information in a forecasting environment.

Following upon previous efforts to associate standard measures of forecast skill to relative economic value, the connection is established between the Clayton skill score and the range of users who realise positive value from the forecasts. It is also shown that, whereas the maximum relative value that can be obtained from a set of forecasts is based on the probabilities conditioned on the observations, the range of users for whom the forecasts provide positive relative value is based on the probabilities conditioned on the forecasts.

In partnership with the Environment Agency, the Met Office has developed a short-period thunderstorm forecasting system based on a conceptual life-cycle model of convective cells. Although originally intended to provide forecasts of intense precipitation, the model provides a mechanism for predicting other forms of severe weather phenomena associated with thunderstorms. This paper investigates the possibility of using GANDOLF to generate a forecast of lightning risk. Model life-cycle stages are compared against observed lightning locations in order to derive a basis for forecasting risk, and this was then tested on data for three different events. The results from this initial investigation seem promising and suggest this type of approach can be effective.

Measurements and estimates of evaporation have been routinely carried out for over a century. In the United Kingdom the most well-known method of estimating evaporation and its derivatives such as soil moisture deficit (SMD) is the Meteorological Office Rainfall and Evaporation Calculation System (MORECS) which is based on the Penman-Monteith equation. Direct measurements of evaporation have become less common in recent years. A comparison of measurements and estimates of evaporation and SMD at a single site and over two catchment areas is presented in this paper. Measurements of actual evaporation from a grassed lysimeter have been achieved for the period 1995-98 and they agree well with catchment losses over the same time period in two natural catchments, the Upper Brue and Upper Cary. In contrast to this, MORECS estimates of actual evaporation are different by an average of +20% for the Upper Brue catchment and +27% for the Upper Cary catchment. The largest difference is nearly +40% for the Upper Cary catchment. Similarly, there are substantial differences in the estimates of SMD, often up to 50 mm. When local rainfall is used together with MORECS estimates of potential evaporation the discrepancy is reduced but significant differences remain during much of the growing season, although improvements do occur. The results from this paper will be of great importance to growers, water resource planners, engineers who give flood warnings, and to river flow modellers.

Patterns often sought in meteorological fields are ridge lines or narrow zones of relatively high or low values (e.g. stripes or bands in satellite imagery). A method for the automatic detection of such features is presented, using input fields given on regular grids. The fundamental idea is that a grid point is a plausible position for a significant line where not more than two (out of eight) neighbours exhibit better suitability to lie on that very line. Locations with three or more superior neighbours are considered unsuitable, or at least less qualified, for representing positions of the line. This criterion derives from the concept that a significant line passing through a point normally enters the latter from one of the adjacent points and leaves through another neighbour, with these two special neighbours permissibly having superior values of the appropriate test variable. It is empirically demonstrated for selected applications within the field of air mass analysis (including objective front positioning on the basis of numerical model output) that the identification of points satisfying the formulated ‘2-out-of-8’ criterion is, when linked with simple post-processing steps, sufficient to accomplish a good recognition of the sought patterns.

Historical climate conditions were examined to determine whether climate information could improve decisions concerning the seasonal maintenance and operations of regional outdoor swimming pools in heavily urbanised northeastern Illinois. Key weather-sensitive issues defined for pool companies concern time periods for maintenance (including pool painting), weather limits to pools being open, and hot days which extend hours of pool operation. The specific conditions included the frequency of spring and fall painting periods (defined as dry conditions for two or more days with Tmax ≥18 °C (65 °F) and Tmin ≥ 4 °C (40 °F)); summer inclement weather days (days with precipitation ≥ 2.54 mm (0.10 inch) with not more than 2 consecutive hours of dry conditions during open swimming hours and/or Tmax ≤ 21 °C (70 °F)); and hot days (Tmax ≥ 32 °C (90 °F)) were examined.

Climatic records for the region going back 42 years revealed that there were nearly twice as many fall painting periods as those in the spring, indicating that greater emphasis should be placed on pool painting after the swimming season. The average number of inclement weather days was more than twice the number the company budgeted for at the beginning of each swimming season. Plans to extend swimming hours on hot days involves a risky decision since the number of hot days varies dramatically from year-to-year in the Chicago region. Studies showed that winter negative sea-surface temperature anomalies in the central Pacific were related to an above average number of spring painting periods. Also, a higher number of hot summer days occur following El Niño-classified winters. Results reveal that decision-makers in the swimming pool management industry can improve several management decisions by including climate information.

The turbulent kinetic energy (TKE) in the atmospheric surface layer (ASL) gives a measure of the intensity of turbulence that could be altered or brought about by mechanical generation, by thermal generation, through vertical transport into or away, and through dissipation. TKE is mainly responsible for the transportation of pollutants suspended in the air. In this paper, TKE evolution in the ASL is studied for Kharagpur (22.20° N, 87.18° E) during the summer monsoon by making use of data from a 30 m micrometeorological tower set up as part of the Monsoon Trough Boundary Layer Experiment (MONTBLEX). Under steady state and homogeneous conditions the various terms in the TKE equation are studied for active and non-active phases of the monsoon in 1990. Their day-to-day variations and the budgets are studied at the 8 m and 15 m levels. The study reveals strong day-to-day variation and significant vertical variations within the ASL. Despite being a tropical station, the buoyancy term is much less than the contribution by mechanical generation ostensibly due to the monsoon. There are also differences between active and non-active phases of the monsoon. Mechanical generation by wind shear has been found to be the dominating production term, while dissipation dominates the magnitude of all other terms.

The optimum sowing dates for soybean cv. Gaurav were derived for Jabalpur, Raipur and Gwalior in the state of Madhya Pradesh in central India. Dates were derived based on two strategies: (a) probabilities of rainfall and temperature events using ClimProb, a PC based software package, and (b) the CROPGRO Soybean v3.0 crop growth simulation model. In Madhya Pradesh, the optimum sowing dates for multiple cropping, with the first crop as soybean under rainfed conditions, are between weeks 25 and 27, while the optimum sowing dates for rainfed mono-cropping are between weeks 28 and 29.

Numerical simulations are performed using the Penn State University/ National Center for Atmospheric Research Mesoscale Model (MM5) to study the impact of initial conditions on the super cyclone which hit the coast of Orissa in 1999. Because analysis of the cyclone's circulation was inadequate in the initial fields owing to the coarse resolution of the operational analysis systems and sparse oceanic data coverage, synthetic vortex data were generated using empirical relations and used in the analysis. Four-dimensional data assimilation is performed in order to assimilate the synthetic vortex in the initial stage to the model.

Considerable improvement in the track is obtained by using the synthetic vortex. With better specification of the initial vortex structure, the model successfully simulated the typical tropical cyclone characteristics, such as asymmetries in the wind field: the strongest winds occurred in the east and close to the cyclone's centre, strong wind gradients were found between the centre and the maximum wind region, and there was a slow decrease in wind speed up to the middle troposphere. Despite failing to produce the intense pressure drop observed for this cyclone, the model shows much better cyclone development with enhanced initial condition than the analysis.

A weather radar and processing system has been developed in conjunction with North West Water Ltd., a water utility responsible for the supply of potable water and the treatment of wastewater in the north-west of England. The primary objective has been to develop a radar system which can produce accurate and reliable quantitative estimates of rainfall at a temporal and spatial resolution commensurate with the requirements of urban drainage system modelling. This paper describes procedures for removing ground clutter and adjusting radar estimates of rainfall (using the Probability Matching Method). An archive of stratiform rainfall event data has supported an objective assessment of the radar data quality using a dense gauge network and simulated flow hydrographs for an urban drainage system. The results indicate that the adjusted radar data are of comparable accuracy to the dense raingauge data and are therefore of sufficient accuracy to be used for the management of water resources within an urban environment. The data processing and adjustment procedures have been incorporated into a real-time data processing and display software package (ARTIST) which is briefly described in the paper.

In this study 320 people in Hong Kong were interviewed to assess their understanding and perception of severe weather warnings. The majority of the respondents (72%) received warnings from mass media. Although 99.4% of the interviewees claimed they knew all the warning signals, results indicate that most of them have only a basic understanding of what they mean. The study revealed that the warnings often lack other important information, such as the time of issue, validity period and precautions to be taken. Only 31% of the respondents stated they would take precautions at the issue of warnings, although people aged over 60 tended to be well prepared for the onset of severe weather. Public education is necessary to promote people's understanding of the warnings and awareness of the risks of severe weather.