GEWEX Research Articles

Impact of a climate change on the Rhone river catchment hydrology

Within the framework of the Global Energy and Water Cycle Experiment (GEWEX)/Rhone project, a system has been built to estimate the hydrological budget of the Rhone, one of the major European rivers (with a 86,500 km2 surface area for the French part of the catchment). The methodology is based on three models, one for each component of the hydrometeorological system: The atmospheric parameter analysis, the snow cover, the surface water and energy budget, and the underground water transfer and discharge estimation. This tool has been validated for 14 years (from 1981 to 1994) by comparing the daily river flows simulated by the models with measurements from 145 gauging stations. In this study, the results of the ARPEGE‐Climat general circulation model (GCM) have been used to estimate the climate of the Rhone catchment in 60 years. The perturbation of the air temperature and precipitation amount has been used to modify the actual set of meteorological parameters in order to simulate the hydrological budget of the Rhone river. Vegetation and soil structure are supposed to be identical to current values, which is a strong hypothesis. The river discharge and soil water resources under the climatic scenario are compared with the results of the actual simulation. Strong contrasts in the hydrological response of the catchment are noticeable, depending on the location of the subcatchments and the amount of precipitation. Snow cover is the most sensitive hydrological component to the air temperature increase, and the high mountainous river regimes are strongly modified. When considering the soil water content, it appears that the northern part of the domain stays quite wet, whereas drying is enhanced in the south. The uncertainties in the results are estimated by analyzing the model sensitivity to different simple climatic scenarios. In particular, the analysis brings into light the impact of the downscaling of the GCM results.

Cirrus Parcel Model Comparison Project. Phase 1: The Critical Components to Simulate Cirrus Initiation Explicitly

Abstract The Cirrus Parcel Model Comparison Project, a project of the GCSS [Global Energy and Water Cycle Experiment (GEWEX) Cloud System Studies] Working Group on Cirrus Cloud Systems, involves the systematic comparison of current models of ice crystal nucleation and growth for specified, typical, cirrus cloud environments. In Phase 1 of the project reported here, simulated cirrus cloud microphysical properties from seven models are compared for “warm” (−40°C) and “cold” (−60°C) cirrus, each subject to updrafts of 0.04, 0.2, and 1 m s−1. The models employ explicit microphysical schemes wherein the size distribution of each class of particles (aerosols and ice crystals) is resolved into bins or the evolution of each individual particle is traced. Simulations are made including both homogeneous and heterogeneous ice nucleation mechanisms (all-mode simulations). A single initial aerosol population of sulfuric acid particles is prescribed for all simulations. Heterogeneous nucleation is disabled for a second...

CSE Water and Energy Budgets in the NCEP–DOE Reanalysis II

Abstract During the past several years, the Global Energy and Water Cycle Experiment (GEWEX) continental-scale experiments (CSEs) have started to develop regional hydroclimatological datasets and water and energy budget studies (WEBS). To provide some global background for these regional experiments, the authors describe vertically integrated global and regional water and energy budgets from the National Centers for Environmental Prediction (NCEP)–U.S. Department of Energy (DOE) Reanalysis II (NCEPRII). It is shown that maintaining the NCEPRII close to observations requires some nudging to the short-range model forecast, and this nudging is an important component of analysis budgets. Still, to first order one can discern important hydroclimatological mechanisms in the reanalysis. For example, during summer, atmospheric water vapor, precipitation, evaporation, and surface and atmospheric radiative heating all increase, while the dry static energy convergence decreases almost everywhere over the land region...

Closing the Mackenzie basin water budget, water years 1994/95 to 1996/97

A particularly elusive science objective for the Mackenzie Global Energy and Water Cycle Experiment (GEWEX) Study (MAGS) has been to close the atmospheric moisture budget and rationalize it against the surface water budget at annual or even monthly timescales. The task, while not difficult in principle, is complicated by two factors. First is the importance of basin snow‐cover, soil and water‐body storage in the surface water budget. Month‐to‐month changes in these components are frequently greater than the atmospheric flux terms, for example, during spring snowmelt. Furthermore, there is approximately a six‐week lag before local changes are evident in the discharge at the mouth of the basin. Second, the coarse resolution of all of the supporting data may add significant systematic errors. For example, the two radiosonde soundings per day available to the project are unlikely to account adequately for all the moisture generated locally through evapotranspiration during the summer convective season. This analysis will directly address these two main issues by applying hydrologic and atmospheric computations to assess the storage question, and by using additional soundings at a single site to sample the diurnal signature in atmospheric moisture caused by evapotranspiration. Resulting modifications to the atmospheric moisture and surface water budgets then allow near closure of the MAGS monthly water budget within acceptable error limits.

Thermal features of the Mackenzie basin from NOAA AVHRR observations for summer 1994

A series of mid‐afternoon Advanced Very High Resolution Radiometer (AVHRR) thermal radiance scenes were assembled in order to develop a better understanding of the complex energy and water processes leading to variations in surface temperature. An in‐depth knowledge of the temperature variability is of interest to land surface process modelling and its application to the Mackenzie Global Energy and Water Cycle Experiment (GEWEX) Study (MAGS). Clear‐sky land surface temperatures are estimated by applying a split window technique to remove atmospheric effects. A maximum land surface temperature map of the Mackenzie basin at 1‐km scale for summer 1994 is produced. The patterns are related to land surface features and elevation. The basin's maximum land surface temperature patterns can be subdivided into three land zones (≥ 35°C, 33–34°C and 27–32°C) and a water dominated zone (20.5°C on average). The highest maximum temperature zone (≥35°C) corresponds to a combination of minimal vegetation, drier soils and low terrain. This zone is not in the southern part of the basin as might be speculated in the absence of these data, but in a wide low elevation corridor from west of Great Bear Lake along the Mackenzie River down to 50°N, 120°W. The maximum land surface temperatures tend to decrease with increasing vegetation density and surface moisture; they also decrease with elevation at a rate of –4.5°C km–1. This is confirmed by weather station data. The AVHRR data extend this relationship to the 1200 – 2200 m altitude ranges, where there are no station data. The data suggest that elevation and land cover should be taken into account in the objective analysis (spatial interpolation) of station data.

The water balance climatology of the Mackenzie basin with reference to the 1994/95 water year

This project attempted to develop an accurate baseline climatology for the Mackenzie basin suitable for modelling and other evaluation applications in the Mackenzie GEWEX (Global Energy and Water Cycle Experiment) Study. Particular attention and effort were applied to adjusting the observed station precipitation data in order to minimize systematic measurement errors. Various geostatistical methods were applied to interpolate the station data onto a uniform grid. This resulted in datasets of 50‐km grid square values for mean monthly temperature and monthly total precipitation for the years 1950 to 1997 inclusive. An independent estimate of basin evapotranspiration was derived using an empirical model (Morton, 1983) to generate similar grid square values of monthly total evapotranspiration for the years 1953 to 1996 inclusive. From the grid square datasets, we computed the mean annual basin temperature (T) to be –3.4°C, the mean annual basin precipitation (P) to be 421 mm and the mean annual basin evapotranspiration (E) to be 277 mm. A simple water balance was applied to test the consistency of the P and E fields with the observed basin discharge (Q). For the 24‐year period 1972 to 1995, the mean annual residual (P‐E‐Q) for the water balance was –28.4 mm. This residual is a combination of errors in the three water balance components and the assumption of zero annual storage. It is within the estimation errors associated with the measurement and analysis methods used. Further analysis on the correlation of Q with the total basin net surface moisture supply (P‐E) showed that P and (P‐E) are most strongly correlated with Q with a 3‐month lag, i.e., a discharge water‐year of October–September corresponds best with a (P‐E) year of July–June. In examining the seasonal correlation of T and E with Q, we found that summer T was significantly correlated with annual Q but there was no significant correlation between any seasonal E or annual Q. This suggests that although the Morton model estimates of E provided a reasonable magnitude for the long‐term annual basin water balance, it cannot be considered reliable for year‐to‐year or shorter‐term estimates of the basin evapotranspiration. In examining the 1994/95 water year, it was found to be the lowest discharge year (October–September) in the observed record. This is consistent with the 3‐month lagged climate data year (July–June) which for 1994/95 has the largest (P‐E) anomaly; it is also the driest year since 1950 having the warmest summer months on record and the third lowest precipitation on record. To demonstrate a practical application of the climate datasets generated by this study, we constructed a multilinear regression model for annual (October–September) discharge based on annual (July–June) basin precipitation and summer temperature. The resulting linear model estimated the annual discharge remarkably well, explaining 61% of the variance for this period. Using this model we were able to reconstruct an estimate of annual discharge back to 1950.

Intercomparison and evaluation of cumulus parametrizations under summertime midlatitude continental conditions

AbstractThis study reports the Single‐Column Model (SCM) part of the Atmospheric Radiation Measurement (ARM)/the Global Energy and Water Cycle Experiment (GEWEX) Cloud System Study (GCSS) joint SCM and Cloud‐Resolving Model (CRM) Case 3 intercomparison study, with a focus on evaluation of cumulus parametrizations used in SCMs. Fifteen SCMs are evaluated under summertime midlatitude continental conditions using data collected at the ARM Southern Great Plains site during the summer 1997 Intensive Observing Period. Results from ten CRMs are also used to diagnose problems in the SCMs.It is shown that most SCMs can generally capture well the convective events that were well‐developed within the SCM domain, while most of them have difficulties in simulating the occurrence of those convective events that only occurred within a small part of the domain. All models significantly underestimate the surface stratiform precipitation. A third of them produce large errors in surface precipitation and thermodynamic structures. Deficiencies in convective triggering mechanisms are thought to be one of the major reasons. Using a triggering mechanism that is based on the vertical integral of parcel buoyant energy without additional appropriate constraints results in overactive convection, which in turn leads to large systematic warm/dry biases in the troposphere. It is also shown that a non‐penetrative convection scheme can underestimate the depth of instability for midlatitude convection, which leads to large systematic cold/moist biases in the troposphere.SCMs agree well quantitatively with CRMs in the updraught mass fluxes, while most models significantly underestimate the downdraught mass fluxes. Neglect of mesoscale updraught and downdraught mass fluxes in the SCMs contributes considerably to the discrepancies between the SCMs and the CRMs. In addition, uncertainties in the diagnosed mass fluxes in the CRMs and deficiencies with cumulus parametrizations are not negligible.Similar results are obtained in the sensitivity tests when different forcing approaches are used. Finally, sensitivity tests from an SCM indicate that its simulations can be greatly improved when its triggering mechanism and closure assumption are improved. © Royal Meteorological Society, 2002. J. C. Petch's contribution is Crown copyright.

Observations of Energy Fluxes and Evapotranspiration over Terrestrial Complex Land Covers in the Tropical Monsoon Environment

The surface energy flux balance and total evapotranspiration were estimated using the eddy correlation, and bandpass covariance technique over a tropical monsoon environment within the framework of GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment (GAME). The aim of this present study is to obtain information on the seasonal variation of heat and water vapor exchanges between the atmosphere and terrestrial land cover (complex area) in tropical monsoon environment. The result indicated the daily integrated values of net radiation, sensible heat, latent heat and ground heat flux during the observation period from July 1998 to February 1999 were 10.76 MJ m -2 , 2.32 MJ m -2 , 5.18 MJ m -2 and 0.03 MJ m -2 , respectively. Sensible and latent heat fluxes were the dominant energy partitioning components throughout the year. The seasonal difference in surface fluxes between wet and dry seasons was seen, and the latent heat flux was dominant in the monsoon, corresponding with the increase of specific humidity after frequent precipitation. Whereas the sensible heat flux increased as the surface temperature increased in the absence of rainfall during the dry season. However, the closure of energy balance remained unresolved as with the foregoing experimental studies. The estimated amount to evapotranspiration was 526 mm versus 641 mm of actual precipitation, and accounted for about 80% of the precipitation during this period.

Aircraft observations of surface–atmosphere exchange during and after snow melt for different arctic environments: MAGS 1999

AbstractThe arctic environment, and in particular the Mackenzie Basin, displays a very dynamic interrelationship between the atmosphere and the surface for the different ecosystems represented. The Canadian Twin Otter research aircraft flew a total of 24 grid and long regional transects, over tundra, forest and delta ecosystems, during the period of snow melt (late May–early June) and early summer (early July) as part of the 1999 Mackenzie Area GEWEX (Global Energy and Water Cycle Experiment) Study (MAGS) field campaign. Observations over tundra showed a sharp rise in the sensible heat flux at the onset of melt, reaching a maximum at the end of the melting period similar to those observed in early summer. The latent heat flux showed a more gradual rise from snowmelt to early summer with a Bowen ratio (sensible heat/latent heat) of two during melt. The forested system demonstrated a similar gradual rise in the latent heat flux, whereas the sensible heat flux was already high with Bowen ratios reaching three at the start of the observation period in late May. The gradual rise in latent heat flux can be tied to gradual thawing of the root zone and the onset of photosynthesis activity. The relatively low solar elevation angle and earlier start of snow melt along the regional transect may account for the much larger sensible heat flux. An analysis of the turbulent coherent structures indicates that the spatial density of structures for both latent heat and sensible heat increases strongly with season, from snow melt into the early summer conditions. This has implications for sampling criteria and optimum flux averaging period.There are distinct differences in energy partitioning between the various arctic ecosystems. At the beginning of the observation period, almost all the net radiation over the delta and tundra regions is utilized in non‐turbulent form, whereas the forested areas use less than 50%. Model simulations of the ground heat flux showed observed diurnal imbalances and suggest that the magnitudes depend on the position of the permafrost table and may partially account for the large non‐turbulent energy. Preliminary results from the Canadian MC2 model using the MAGS aircraft data for diagnosis and validation have identified sensitive model components that may merit further investigation. The findings from this study will help to fill gaps in our knowledge about surface–atmosphere interactions in arctic environments, particularly during snow melt, and broadens our contemporary view of evapotranspiration dynamics of wet surfaces. Copyright © 2001 John Wiley & Sons, Ltd.

The Baltic Sea Experiment (BALTEX): A European Contribution to the Investigation of the Energy and Water Cycle over a Large Drainage Basin

The Baltic Sea Experiment (BALTEX) is one of the five continental-scale experiments of the Global Energy and Water Cycle Experiment (GEWEX). More than 50 research groups from 14 European countries are participating in this project to measure and model the energy and water cycle over the large drainage basin of the Baltic Sea in northern Europe. BALTEX aims to provide a better understanding of the processes of the climate system and to improve and to validate the water cycle in regional numerical models for weather forecasting and climate studies. A major effort is undertaken to couple interactively the atmosphere with the vegetated continental surfaces and the Baltic Sea including its sea ice. The intensive observational and modeling phase BRIDGE, which is a contribution to the Coordinated Enhanced Observing Period of GEWEX, will provide enhanced datasets for the period October 1999-February 2002 to validate numerical models and satellite products. Major achievements have been obtained in an improved understanding of related exchange processes. For the first time an interactive atmosphere-ocean-land surface model for the Baltic Sea was tested. This paper reports on major activities and some results.

Diagnosing warm season precipitation over the GCIP region from a GCM and reanalysis

A 45‐year simulation using a global general circulation model (GCM), the National Center for Atmospheric Research (NCAR) Community Climate Model version 3 (CCM3), forced with observed sea surface temperatures (SST), and 39 years of global National Centers for Environmental Prediction (NCEP) reanalyses were analyzed to determine Mississippi River basin warm season (May, June, July or MJJ) wet and dry year composites in the water and energy budgets. Years that have increased MJJ soil moisture over the Global Energy and Water Cycle Experiment (GEWEX) Continental‐Scale International Project (GCIP) region also have high precipitation, lower surface temperature, decreased Bowen ratio, and reduced 500‐hPa geopotential height (essentially reduced MJJ ridging). The reverse is true for years that have reduced MJJ soil moisture. Wet years are also accompanied by a general increase in moisture transport from the Gulf of Mexico into the central United States. There is some indication (though weaker) that soil moisture may then affect precipitation and other quantities and be affected in turn by 500‐hPa geopotential heights. The correlations are somewhat low, however, demonstrating the difficulty in providing definitive physical links between the remote and local effects. Analysis of two individual years with an extreme wet event (1993) and an extreme dry event (1988) yields the same general relationships as with the wet and dry composites. The composites from this study are currently serving as the basis for a series of experiments aimed at determining the predictability of the land surface and remote SST on the Mississippi River basin and other large‐scale river basins.

BALTEX precipitation analysis: results from the BRIDGE preparation phase

The Baltic Sea Experiment (BALTEX) is the European contribution to the Global Energy and Water Cycle Experiment (GEWEX). During the preparation phase of the BALTEX main experiment BRIDGE a Precipitation Correction and Analysis (PCA) model has been designed and was tested using 3 years (August 1995 – December 1998) of about 4 000 rain gauge observations collected by the BALTEX Meteorological Data Centre (BMDC). The PCA model consists of two parts: (1) a bias correction and (2) a geostatistical module. The dynamic bias correction reduces the systematic underestimation of the rain gauges due to wind-induced, evaporation and wetting losses taking instrument-specific properties as well as additional information from synoptic observations into account. The mean correction factor has a maximum in February (1.25 – 1.50) and a minimum in August (1.02 – 1.05). The geostatistical module of the PCA model consists of an ordinary block kriging algorithm to estimate area averaged precipitation values on the grid of the meso-scale model REMO (spatial resolution: 16 degree or 18 km). Results, to be operationally produced during BRIDGE, will be daily, monthly and annual meso-scale precipitation fields based on quality checked, bias corrected rain gauge measurements.

A GCSS model intercomparison for a tropical squall line observed during toga‐coare. II: Intercomparison of single‐column models and a cloud‐resolving model

AbstractThis paper presents single‐column model (SCM) simulations of a tropical squall‐line case observed during the Coupled Ocean‐Atmosphere Response Experiment of the Tropical Ocean/Global Atmosphere Programme. This case‐study was part of an international model intercomparison project organized by Working Group 4 ‘Precipitating Convective Cloud Systems’ of the GEWEX (Global Energy and Water‐cycle Experiment) Cloud System Study.Eight SCM groups using different deep‐convection parametrizations participated in this project. The SCMs were forced by temperature and moisture tendencies that had been computed from a reference cloud‐resolving model (CRM) simulation using open boundary conditions. The comparison of the SCM results with the reference CRM simulation provided insight into the ability of current convection and cloud schemes to represent organized convection. The CRM results enabled a detailed evaluation of the SCMs in terms of the thermodynamic structure and the convective mass flux of the system, the latter being closely related to the surface convective precipitation. It is shown that the SCMs could reproduce reasonably well the time evolution of the surface convective and stratiform precipitation, the convective mass flux, and the thermodynamic structure of the squall‐line system. The thermodynamic structure simulated by the SCMs depended on how the models partitioned the precipitation between convective and stratiform. However, structural differences persisted in the thermodynamic profiles simulated by the SCMs and the CRM. These differences could be attributed to the fact that the total mass flux used to compute the SCM forcing differed from the convective mass flux. The SCMs could not adequately represent these organized mesoscale circulations and the microphysicallradiative forcing associated with the stratiform region. This issue is generally known as the ‘scale‐interaction’ problem that can only be properly addressed in fully three‐dimensional simulations.Sensitivity simulations run by several groups showed that the time evolution of the surface convective precipitation was considerably smoothed when the convective closure was based on convective available potential energy instead of moisture convergence. Finally, additional SCM simulations without using a convection parametrization indicated that the impact of a convection parametrization in forced SCM runs was more visible in the moisture profiles than in the temperature profiles because convective transport was particularly important in the moisture budget.

A midterm report on the GEWEX Continental‐Scale International Project (GCIP)

The GEWEX Continental‐Scale International Project (GCIP) is being carried out in the Mississippi River Basin under the auspices of the World Climate Research Program and its Global Energy and Water Cycle Experiment (GEWEX). This paper provides a brief history of GCIP's development and its mission and objectives. The scientific achievements of GCIP are then reviewed against each of these objectives. The paper concludes with a brief discussion of options for the period beyond 2000 after the current phase of the project is completed.

Assessment of land‐surface energy budgets from regional and global models

The surface energy budgets estimated from the 0‐ to 12‐hour forecasts of three operational model suites and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis are analyzed at local to continental scales. The models are (1) the Eta model, (2) the Mesoscale Analysis and Prediction System (MAPS), and (3) the Global Environmental Multiscale (GEM) model. The first two are regional, while the third one is global with a variable grid with a resolution over North America that is equivalent to that of the regional models. This assessment of one summer month (August 1997) and one winter month (January 1998) has the purpose of estimating the reliability of the surface energy budgets within the context of the Global Energy and Water Cycle Experiment (GEWEX) Continental‐Scale International Project (GCIP) goals. Satellite estimates were used to evaluate the downward short wave radiation at the surface, while measurements from the southern Great Plains region were used to evaluate the model computed surface energy budget estimates. The results show that the surface short wave radiation biases of the models are widespread and of the order of 25–50 W m−2 and averaging over larger areas does not help reduce the differences. These biases are compensated by the other long and short wave radiation terms so that the resulting errors in the net radiation are smaller. During August 1997, continental east‐west gradients of latent heat flux and Bowen ratio were surprisingly dissimilar among models. Still, the Bowen ratio estimated from the Eta and GEM models was close to observations over the southern Great Plains region, while both the Reanalysis and MAPS had ratios that at least doubled the observed ones. In the case of MAPS a revised latent heat flux formulation was introduced in fall 1997, and, subsequently, for January 1998, estimates were closer to the other models' estimates. However, during January 1998 all models had difficulties reproducing the Bowen ratios from observations. Further, daily time series showed that models' estimates also tended to miss the amplitude of the day‐to‐day variability. It is conceivable that this may be the result of difficulties in parameterizing the total cloud cover, and, particularly, attenuation by clouds may still be insufficient.

Runoff simulation in the upper warta catchment during 1992 and 1993

The land-surface parametenzation model SEWAB (Surface Energy and Water Balance) has been developed to provide the lower boundary condition for atmospheric models. It solves the coupled system of the Surface Energy and Water Balance equations considering partly vegetated surfaces. Within the soil column the vertical diffusion equation for soil temperature and soil moisture are solved semi-implicitely at a variable number of layers. SEWAB is a parameterization to be used to link the atmospheric and hydrological models e.g. in the Baltic Sea Experiment (BALTEX), a continental scale experiment under the Global Energy and Water Cycle Experiment (GEWEX). The catchment under consideration is first overlaid by a grid net, e.g. of the atmospheric model, then SEWAB is applied to each grid box. Runoff calculated from each grid box is the input to a hydrological model describing the horizontal transport to and within the river network on a daily bases. Calculated streamflow can be compared to measurements at gauging stations, validating not only the model results from the atmospheric model but also providing daily river runoff to ocean models. In this paper the model and methods are briefly introduced. Results are shown for the upper Warta catchment using measured meteorological data to force the model.

ISCCP_DX cloud products in support of BALTEX

Within the framework of BALTEX (Baltic Sea Experiment), the European GEWEX (Global Energy and Water Cycle Experiment) regional study, a regional atmospheric model REMO (horizontal resolution 18km) is used at GKSS to study the exchange of energy and water between surface and atmosphere over the Baltic sea catchment area. For such numerical model calculations of water and energy balances to be reliable, ideally the model should be validated over the whole computational domain with high spatiotemporal resolution, for which satellite data are particularly well suited. The International Satellite Cloud Climatology Project (ISCCP) has been for more than a decade collecting data of the operational satellites. While those data in general are used to improve understanding of the cloud and radiation problems with a typical resolution of 280×280 km 2, there have to be new studies initiated focusing on how to use these data for the retrieval of regional radiation budget products related to the spatiotemporal scales of the regional models. We compare results of our REMO predictions against products of the ISCCP_DX data. These products are derived for individual instantaneous satellite field of views of about 4km 2 sampled horizontally every 30km with a 3 hourly time resolution. To compare ISCCP_DX products against model predictions for a 18×18km 2 grid cell we take into account the ISCCP sampling within such a grid cell to retain temporal and spatial information in model output and observations.

The Mackenzie GEWEX Study: The Water and Energy Cycles of a Major North American River Basin

The Mackenzie River is the largest North American source of freshwater for the Arctic Ocean. This basin is subjected to wide fluctuations in its climate and it is currently experiencing a pronounced warming trend. As a major Canadian contribution to the Global Energy and Water Cycle Experiment (GEWEX), the Mackenzie GEWEX Study (MAGS) is focusing on understanding and modeling the fluxes and reservoirs governing the flow of water and energy into and through the climate system of the Mackenzie River Basin. MAGS necessarily involves research into many atmospheric, land surface, and hydrological issues associated with cold climate systems. The overall objectives and scope of MAGS will be presented in this article.

Report endorses climate study, recommends several research foci

A major study to understand climate variability and predict climate change should proceed in the same direction, a National Research Council (NRC) panel has recommended. The panel also urged the implementation of a number of future research activities. The study, known as the Continental‐Scale Intercomparison Project (GCIP), the first of five continental‐scale projects of the Global Energy and Water Cycle Experiment (GEWEX), began in 1990.Recent efforts to study climate have emphasized the importance of improved understanding of many aspects of the hydrologic cycle and the exchange of energy and water at the atmosphere‐surface interface. To address these issues within the context of the Mississippi River basin, the World Climate Research Programme established the GEWEX GCIP. The NRC established a panel specifically to evaluate and provide scientific leadership and guidance on the scientific strategies, plans, and priorities of the GEWEX Program. This panel's report, “GCIP: A Review of Progress and Opportunities,” also highlighted the major accomplishments of the study so far. It was released June 8 at the GCIP Mississippi River Hydrometeorology Conference in St. Louis, Mo.

The Baltic Sea Experiment BALTEX: A brief overview and some selected results of the authors

The mechanisms responsible for the transfer of energy and water within the climate system are under worldwide investigation within the framework of the Global Energy and Water Cycle Experiment (GEWEX) to improve the predictability of natural and man-made climate changes at short and long ranges and their impact on water resources. Five continental-scale experiments have been established within GEWEX to enable a more complete coupling between atmospheric and hydrological models. One of them is the Baltic Sea Experiment (BALTEX). In this paper, the goals and structure of BALTEX are outlined. A short overview of measuring and modelling strategies is given. Atmospheric and hydrological model results of the authors only are presented. These include also the validation of precipitation using station measurements as well as validation of modelled cloud cover with cloud estimates from satellite data. Furthermore, results of a large-scale grid based hydrological model to be coupled to atmospheric models are presented. This research has never been possible without the contribution of research groups and operational institutions from all 10 member countries. We concentrate here on results obtained at the GKSS research center.