Mesoscale Regions Research Articles

Quantifying Land Surface Temperature Variability for Two Sahelian Mesoscale Regions during the Wet Season

Abstract Land–atmosphere feedbacks play an important role in the weather and climate of many semiarid regions. These feedbacks are strongly controlled by how the surface responds to precipitation events, which regulate the return of heat and moisture to the atmosphere. Characteristics of the surface can result in both differing amplitudes and rates of warming following rain. Spectral analysis is used to quantify these surface responses to rainfall events using land surface temperature (LST) derived from Earth observations (EOs). The authors analyzed two mesoscale regions in the Sahel and identified distinct differences in the strength of the short-term (<5 days) spectral variance, notably, a shift toward lower-frequency variability in forest pixels relative to nonforest areas and an increase in amplitude with decreasing vegetation cover. Consistent with these spectral signatures, areas of forest and, to a lesser extent, grassland regions were found to warm up more slowly than sparsely vegetated or barren pixels. The authors applied the same spectral analysis method to simulated LST data from the Joint UK Land Environment Simulator (JULES) land surface model. A reasonable level of agreement was found with the EO spectral analysis for two contrasting land surface regions. However, JULES shows a significant underestimate in the magnitude of the observed response to rain compared to EOs. A sensitivity analysis of the JULES model highlights an unrealistically high level of soil water availability as a key deficiency, which dampens the models response to rainfall events.

Limited-are a modelling of stratocumulus over South-Eastern Pacific

Abstract. This paper presents application of the Weather Research and Forecasting (WRF) model to limited-area modeling of atmospheric processes over the subtropical south-eastern Pacific, with the emphasis on the stratocumulus-topped boundary layer. The simulations cover a domain from the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) field project conducted in the subtropical south-eastern Pacific in October and November 2008. We focus on a day where the UK's BAe-146 research aircraft encountered Pockets of Open Cells (POCs) at the very western edge of its flight track, rather than on the entire campaign as investigated in previous limited-area modeling studies. Model results are compared to aircraft observations with the main conclusion that the simulated stratocumulus-topped boundary layer is significantly too shallow. This appears to be a combination of an already too shallow boundary layer in the dataset used to provide initial and lateral boundary conditions, and the inability of the WRF model to increase the boundary-layer height. Several sensitivity simulations, applying different subgrid-scale parameterizations available in the model, a larger computational domain and longer simulations, as well as a different dataset providing initial and lateral boundary conditions were all tried to improve the simulation. These changes appeared to have a rather small effect on the results. The model does simulate the formation of mesoscale cloud-free regions that one might consider similar to Pockets of Open Cells observed in nature. However, formation of these regions does not seem to be related to drizzle-induced transition from open- to closed-cell circulations as simulated by LES models. Instead, the cloud-free regions appear to result from mesoscale variations of the lower-tropspheric vertical velocity. Areas of negative vertical velocity with minima (a few cm s−1) near the boundary layer top seem to induce direct evaporation of the cloud layer. It remains to be seen in LES studies whether the mechanism seen in the model is realistic or if it is simply an artifact of interactions between resolved and parameterized processes.

Climatic parameters of wind-field variability in the Black Sea region: Numerical reanalysis of regional atmospheric circulation

A reanalysis of atmospheric circulation in the Black Sea region is performed with a high spatial resolution of 25 × 25 km for the period from 1958 to 2001. Climatic wind speed fields are estimated, as are their spatial structure and seasonal variability. Mesoscale regions of cyclonic and anticyclonic speed vorticity, which are connected with edge effects and orography, are distinguished. To single out the monsoon mechanism in the annual votricity cycle, numerical experiments on the sensitivity that the regional atmospheric circulation has to the sea-surface temperature perturbations have been carried out. Large-scale regional peculiarities of the surface wind field are considered for different seasons. The vorticity of the surface wind speed and strength is assessed. Large annual average values of the vorticity are obtained which are comparable with the range of seasonal variability; they evidence the defining role that wind plays in the generation and seasonal variability, as well as the average cyclonic water circulation in the Black Sea.

Distant Effects of a Recurving Tropical Cyclone on Rainfall in a Midlatitude Convective System: A High-Impact Predecessor Rain Event*

Abstract Recent research has identified predecessor rain events (PREs), which are mesoscale regions of heavy rainfall that occur ∼1000 km poleward and downshear of recurving tropical cyclones (TCs). PREs typically occur 24–36 h prior to the arrival of the main rain shield associated with the TC, and frequently result in damaging flooding. A distinguishing feature of a PRE is that it is enhanced by a broad region of deep tropical moisture directly associated with the TC that is transported well poleward ahead of the TC. This study will quantify the effects of the tropical moisture from one TC on a record-breaking rain and flood event over the northern Great Plains and southern Great Lakes region on 18–19 August 2007. In this event, which occurred ahead of TC Erin, a southerly stream of deep tropical moisture (precipitable water values >50 mm) moved poleward and intersected a northwest–southeast-oriented quasi-stationary baroclinic zone beneath the equatorward entrance region of an upper-level jet streak. A slow-moving mesoscale convective system (MCS) developed and produced widespread heavy rainfall, with local amounts exceeding 380 mm that resulted in historic flooding in Minnesota and Wisconsin. Observations and numerical simulations using the Advanced Research Weather Research and Forecasting model (ARW-WRF) indicate that low-level frontogenesis was maximized during the overnight hours of 19 August 2007 and provided the forcing for vigorous ascent during the mature stage of the PRE. A control simulation, which included the poleward transport of TC Erin-related moisture, reproduced the extreme rainfall amounts, although the simulated rainfall was displaced from where it was observed. A sensitivity simulation in which the moisture associated with TC Erin was removed (referred to as “NOPLUME”) shows reduced convective available potential energy (CAPE) in the inflow region of the PRE and a less vigorous MCS. In all, there was an approximately 50% reduction in the maximum precipitation amount and a 25% reduction in the total precipitation from the control simulation to the NOPLUME run. Or, considered in the context of rainfall enhancement by the Erin-related moisture, there was a near doubling of the maximum amount and a 33% increase in the total rainfall. The extent of these differences underscores the importance of moisture originating from TC Erin in transforming a heavy rain event into a high-impact, record-breaking rain event.

Modification of inertial oscillations by the mesoscale eddy field

The modification of near‐surface near‐inertial oscillations (NIOs) by the geostrophic vorticity is studied globally from an observational standpoint. Surface drifter are used to estimate NIO characteristics. Despite its spatial resolution limits, altimetry is used to estimate the geostrophic vorticity. Three characteristics of NIOs are considered: the relative frequency shift with respect to the local inertial frequency; the near‐inertial variance; and the inverse excess bandwidth, which is interpreted as a decay time scale. The geostrophic mesoscale flow shifts the frequency of NIOs by approximately half its vorticity. Equatorward of 30°N and S, this effect is added to a global pattern of blue shift of NIOs. While the global pattern of near‐inertial variance is interpretable in terms of wind forcing, it is also observed that the geostrophic vorticity organizes the near‐inertial variance; it is maximum for near zero values of the Laplacian of the vorticity and decreases for nonzero values, albeit not as much for positive as for negative values. Because the Laplacian of vorticity and vorticity are anticorrelated in the altimeter data set, overall, more near‐inertial variance is found in anticyclonic vorticity regions than in cyclonic regions. While this is compatible with anticyclones trapping NIOs, the organization of near‐inertial variance by the Laplacian of vorticity is also in very good agreement with previous theoretical and numerical predictions. The inverse bandwidth is a decreasing function of the gradient of vorticity, which acts like the gradient of planetary vorticity to increase the decay of NIOs from the ocean surface. Because the altimetry data set captures the largest vorticity gradients in energetic mesoscale regions, it is also observed that NIOs decay faster in large geostrophic eddy kinetic energy regions.

Predecessor Rain Events ahead of Tropical Cyclones

Abstract Twenty-eight predecessor rain events (PREs) that occurred over the United States east of the Rockies during 1995–2008 are examined from a synoptic climatology and case study perspective. PREs are coherent mesoscale regions of heavy rainfall, with rainfall rates ≥100 mm (24 h)−1, that can occur approximately 1000 km poleward of recurving tropical cyclones (TCs). PREs occur most commonly in August and September, and approximately 36 h prior to the arrival of the main rain shield associated with the TC. A distinguishing feature of PREs is that they are sustained by deep tropical moisture that is transported poleward directly from the TC. PREs are high-impact weather events that can often result in significant inland flooding, either from the PRE itself or from the subsequent arrival of the main rain shield associated with the TC that falls onto soils already saturated by the PRE. The composite analysis shows that on the synoptic-scale, PREs form in the equatorward jet-entrance region of a 200-hPa jet on the western flank of a 925-hPa equivalent potential temperature ridge located east of a 700-hPa trough. On the mesoscale, PREs occur in conjunction with low-level frontogenetical forcing along a baroclinic zone where heavy rainfall is focused. A case study analysis was conducted of a PRE ahead of TC Erin (2007) that produced record-breaking rainfall (>250 mm) from southern Minnesota to Lake Michigan. This analysis highlighted the importance of frontogenetical forcing along a low-level baroclinic zone in the presence of deep tropical moisture from TC Erin in producing a long-lived, quasi-stationary mesoscale convective system.

The effects of mesoscale regions of precipitation on the ionospheric dynamics, electrodynamics and electron density in the presence of strong ambient electric fields

Abstract. We have developed a new high resolution two-dimensional model of the high latitude ionosphere in which nonlinear advection terms are closely coupled with the electrodynamics. The model provides a self-consistent description of the ionospheric feedback on the electrodynamical perturbations produced by auroral arc-related particle precipitation in regions with strong ambient electric fields. We find in particular that a heretofore neglected ion Pedersen advection term can introduce considerable changes in the electron density profile, the current density distribution, the conductivities and the electron temperatures. We find that the convective effects can carry the ionisation more than 150 km outside the precipitation region in a few minutes, with attendant large changes in the current distribution and E-region densities that become enhanced outside the region of particle precipitation. The production of a tongue of ionisation that slowly decays outside the auroral boundaries contrasts with the sharp geometric cut-off and associated stronger current densities found in previous studies.

Estimating Local Memory of Tropical Cyclones through MPI Anomaly Evolution

Abstract This study examines the local memory of atmospheric and oceanic changes associated with a tropical cyclone (TC). The memory is quantified through anomalous maximum potential intensity (MPI) evolution for 20 days prior to the arrival of a TC through 60 days after the TC passage. The local MPI weakens and is not restored to the evolving climatology until well after the TC has departed. Stabilization occurs through warming of the atmosphere and cooling of the ocean surface on different time scales. The time scale of MPI stabilization following TC passage is approximately 30–35 days for a tropical storm to 50–60 days for a category 3–5 hurricane, with significant storm-specific and basin-specific variability. The atmospheric stabilization (warming with respect to SST) begins with TC arrival and continues for approximately 7–10 days after passage, when the troposphere cools below normal. The rewarming of SST and the subsequent rewarming of the atmosphere occurs within approximately 35 days for all intensities, despite a positive (weakened) MPI anomaly through two months. This suggests that the atmosphere retains anomalous warmth beyond what can be attributable to sensible heating from the rewarmed SST. The maintenance of a positive MPI anomaly beyond 35 days is thus attributed to a feedback on larger scales that requires considerable further research. A TC’s passage through a region does not always lead to a weakening of the MPI. In regions poleward of the sharp SST gradient, the MPI one month after TC passage is often several millibars stronger than climatology. There are also mesoscale regions of destabilization one month after TC passage that may result partially from salinity changes driven by oceanic mixing as well as changes in precipitation and evaporation.

Banded Convection Caused by Frontogenesis in a Conditionally, Symmetrically, and Inertially Unstable Environment

Abstract Several east–west-oriented bands of clouds and light rain formed on 20 July 2005 over eastern Montana and the Dakotas. The cloud bands were spaced about 150 km apart, and the most intense band was about 20 km wide and 300 km long, featuring areas of maximum radar reflectivity factor of about 50 dBZ. The cloud bands formed poleward of an area of lower-tropospheric frontogenesis, where air of modest convective available potential energy was being lifted. During initiation and maintenance of the bands, mesoscale regions of dry symmetric and inertial instability were present in the region of the bands, suggesting a possible mechanism for the banding. Interpretation of the extant instabilities in the region of the bands was sensitive to the methodology to assess the instability. The release of these instabilities produced circulations with enough vertical motion to lift parcels to their lifting condensation level, resulting in the observed cloud bands. A high-resolution, numerical weather prediction model demonstrated that forecasting these types of events in such real-time models is possible, although the timing, evolution, and spacing of the bands were not faithfully reproduced. This case is compared to two previous cases in the literature where banded convection was associated with a combination of conditional, symmetric, and inertial instability.

Environmental Control of Cloud-to-Ground Lightning Polarity in Severe Storms

Abstract In this study, it is hypothesized that the mesoscale environment can indirectly control the cloud-to-ground (CG) lightning polarity of severe storms by directly affecting their structural, dynamical, and microphysical properties, which in turn directly control cloud electrification and ground flash polarity. A more specific hypothesis, which has been supported by past observational and laboratory charging studies, suggests that broad, strong updrafts and associated large liquid water contents in severe storms lead to the generation of an inverted charge structure and enhanced +CG lightning production. The corollary is that environmental conditions favoring these kinematic and microphysical characteristics should support severe storms generating an anomalously high (>25%) percentage of +CG lightning (i.e., positive storms) while environmental conditions relatively less favorable should sustain storms characterized by a typical (≤25%) percentage of +CG lightning (i.e., negative storms). Forty-eight inflow proximity soundings were analyzed to characterize the environment of nine distinct mesoscale regions of severe storms (4 positive and 5 negative) on 6 days during May–June 2002 over the central United States. This analysis clearly demonstrated significant and systematic differences in the mesoscale environments of positive and negative storms, which were consistent with the stated hypothesis. When compared to negative storms, positive storms occurred in environments associated with a drier low to midtroposphere, higher cloud-base height, smaller warm cloud depth, stronger conditional instability, larger 0–3 km AGL wind shear, stronger 0–2 km AGL storm relative wind speed, and larger buoyancy in the mixed-phase zone, at a statistically significant level. Differences in the warm cloud depth of positive and negative storms were by far the most dramatic, suggesting an important role for this parameter in controlling CG lightning polarity. In this study, strong correlations between the mesoscale environment and CG lightning polarity were demonstrated. However, causality could not be verified due to a lack of in situ observations to confirm the hypothesized microphysical, dynamical, and electrical responses to variations in environmental conditions that ultimately determined the dominant CG polarity. Future observational field programs and cloud modeling studies should focus on these critical intermediary processes.

Oscillatory behavior of monsoon rainfall over Sri Lanka during the late 19th and 20th centuries and its relationships to SSTs in the Indian Ocean and ENSO

In this study, we have analyzed the temporal oscillations of precipitation in meso-scale zones of Sri Lanka to examine potential existence of periodic oscillatory behavior in rainfall. Only a few statistically significant cycles were identified: a 3.5-year cycle in most of central Sri Lanka during the January–March rainfall regime and a cycle of the same length in southwestern Sri Lanka during the October regime. A 2.1-year cycle marks the northeastern parts of Sri Lanka during the December/April contrast rainfall regime. This cycle is shown to be strongly related to Quasi-Biennial Oscillation. October and November rainfall are found to be coupled with ENSO fluctuations, and on average, more than 900 mm more rainfall is observed per month over all stations during El Nino than during La Nina years. Analysis of relationships between the observed meso-scale rainfall regions and the Sea Surface Temperatures (SSTs) in the Indian Ocean north of the Equator showed that the northern Indian Ocean can be divided into three particular regions based on similarity in the SST fluctuations: (a) a region with cool upwelling water, (b) non upwelling water, and (c) the Indian Ocean Warm Pool. We found that there are no statistically significant relationships between the observed SST regions in the Indian Ocean and the meso-scale precipitation patterns in Sri Lanka.

Adaptive resolution scheme for efficient hybrid atomistic-mesoscale molecular dynamics simulations of dense liquids

The adaptive resolution scheme (AdResS) for efficient hybrid particle-based atomistic/mesoscale molecular dynamics (MD) simulations recently introduced by us, [J. Chem. Phys. 123, 224106 (2005)] is extended to high density molecular liquids with spherical boundaries between the atomistic and mesoscale regions. The key feature of this approach is that it allows for a dynamical change of the number of molecular degrees of freedom during the course of a MD simulation by an on-the-fly switching between the atomistic and mesoscopic levels of detail. Pressure and density variations occurring at the atomistic/mesoscale boundary in the original version are considerably reduced employing the improved methodology presented here.

The Shared Mobile Atmospheric Research and Teaching Radar: A Collaboration to Enhance Research and Teaching

A group of scientists from three universities across two different states and from one federal research laboratory joined together to build and deploy two mobile C-band Doppler weather radars to enhance research and promote meteorological education. This 5-yr project led to the development of the Shared Mobile Atmospheric Research and Teaching (SMART) radar coalition that built the first mobile C-band Doppler weather radar in the United States and also successfully deployed the first mobile C-band dual-Doppler network in a landfalling hurricane. This accomplishment marked the beginning of an era in which high temporal and spatial resolution precipitation and dual-Doppler wind data over mesoscale (~100 km) regions can be acquired from mobile ground-based platforms during extreme heavy rain and high-wind events. In this paper, we discuss the rationale for building the mobile observing systems, highlight some of the challenges that were encountered in creating a unique multiagency coalition, provide examples of how the SMART radars have contributed to research and education, and discuss future plans for continued development and management of the radar facility, including how others may use the radars for their own research and teaching programs. The capability of the SMART radars to measure winds in nonprecipitating environments, to capture rapidly evolving, short-lived, small-scale tornadic circulations, and to sample mesoscale regions with high spatial resolution over broad regions of heavy rainfall is demonstrated. Repeated successful intercepts provide evidence that these radars are capable of being used to study a wide range of atmospheric phenomena.

Combining Argo and remote-sensing data to estimate the ocean three-dimensional temperature fields—a first approach based on simulated observations

The study aims to analyze the contribution of the combination of high-resolution sea level and sea surface temperature satellite data with accurate but sparse in situ temperature profile data as given by Argo to the reconstruction of the large-scale, monthly mean, 200-m depth temperature fields. The main issue is to reconstruct instantaneous temperature fields at high temporal and spatial resolution and thus improve the representation of the large-scale and low-frequency temperature fields at the given depth. The method is developed and presented for the temperature field at 200-m depth but can be applied to any depth and also to the salinity field. The study uses outputs and profiling float simulations derived from a state-of-the-art, eddy-resolving (1/6°-resolution) primitive equation model of the North Atlantic. Synthetic 200-m temperatures are first derived from simulated altimeter and SST data through a multiple linear regression; they are then combined with individual Argo 200-m simulated temperatures. The optimal merging uses an objective analysis method that takes into account analyzed errors on the observations and, particularly, correlated errors on synthetic temperatures deduced from remote-sensing data. Results indicate that the optimal combination is instrumental in reducing the aliasing due to the mesoscale variability and in adjusting the high-resolution combined fields to the in situ data. The rms of mapping error of the large-scale and low-frequency temperature fields at 200-m depth is largely reduced (by a factor of 4 in large mesoscale variability regions) when combining both data types, as compared to the results obtained using only in situ profiles.

Krill ( Euphausia superba ) recruitment indices from the western Antarctic Peninsula: are they representative of larger regions?

This study presents data on krill demography west of the Antarctic Peninsula covering many years since 1982. The recruitment indices are compared with those for other mesoscale study regions collected over the last 25 years. We use these data to investigate whether results from such mesoscale surveys are representative of large-scale stocks or regional populations. Generally, the proportional recruitment indices for 1- (R1) and 2-year-old (R2) krill differ substantially between years for a given area. However, indices were in conformity with the results from other regional scientific surveys. Recruitment indices showed a significant correlation for age-class 1 krill between scientific surveys from the northern Bellingshausen Sea, the Elephant Island area and South Georgia. The correlation becomes weaker for R2 recruitment indices. There was no correlation between krill recruitment indices from Atlantic and Indian Ocean survey sites. Problems of single-year outliers from Elephant Island are discussed, as well as the problem of "undersized" length classes of the age-1 group that occur in the samples of some years.

The Region of Large Sea Surface Height Variability in the Southeast Pacific Ocean

Satellite altimeter observations of sea surface height (SSH) show an extensive triangular region of high variability in the southeastern Pacific. The region is unusual in two ways. First, it appears to have a horizontal correlation scale that is much larger than that associated with the mesoscale eddy-rich regions of the deep ocean. Second, the feature appears to reflect the shape of the underlying topography. Previous computer studies have suggested that it is a Rossby wave trapped by topography. Here detailed results are presented from a study that used a high-resolution global ocean model forced by 6-hourly ECMWF winds. The empirical orthogonal modes of the region are calculated, and it is shown that 29% of the SSH variance is due to a single mode with a similar shape to the region of high variability. The time series of the mode is correlated against the local Ekman pumping, and it is shown that the largest correlation is obtained when the lag is approximately 24 hours and the wind curl is averaged over a region roughly the size of the mode itself. The response function relating the amplitude of the mode time series to the amplitude of the forcing is calculated and is found to be dominated by a resonance at zero frequency and a decay time of 2.7 days. The results indicate that the feature is a highly damped geostrophic mode of the ocean.

How realistic is the high‐frequency signal of a 0.1° resolution ocean model?

This paper describes the results from a comparative wavelet analysis of a 0.1, 40‐level Parallel Ocean Program model simulation of the North Atlantic with coincident in situ measurements of sea surface height (SSH) and temperature. The wavelet analysis is used to examine the realism of the surface's variability and its high‐frequency signals (less than a year). Along the coast, it shows that the model's simulated fields of SSH are realistic with the correlations to tide gauge measurements on the order of 0.8. The wavelet spectra show that the model replicates the observations' frequency space. Comparisons of the model's temperatures to temperatures from NOAA buoys north and south of the Gulf Stream show that, while not replicating the location of mesoscale features all the time, the model's energy in the strong mesoscale regions compares favorably to data. Due to the TOPEX/POSEIDON's (T/P) sampling, which requires large areal averages and because of the model's spontaneous eddy field, the evaluation of the simulation in the open ocean is less conclusive. The model does show similarities to the T/P data at high latitudes where the sampling by the sensor is denser and also on the eastern side of the basin with its lower mesoscale activity. Spatially, there are similarities in the amplitude of the signals between the model and the observations in areas with a significant signal in a given spectral band.

Three-Dimensional Cubic Mesoporous Structures of SBA-12 and Related Materials by Electron Crystallography

The chemical potential difference between homopolymer fractions in block copolymers can be readily used to selectively design, and cooperatively assemble, inorganic species into highly ordered three-dimensional (3d) periodic composite arrays of separated mesoscale regions. The actual details and symmetry of these regions and their long-range order can only be determined by 3d imaging and analysis with high-resolution electron microscopy (HREM). Of particular interest is the differentiation between configurations with very similar organization energies, such as the cubic and hexagonal (SBA-2) closed-packed structures. Mesoporous silica SBA-12 and functionalized SBA-12 (SH-SBA-12) have been synthesized from the 3-mercaptopropyl group by using nonionic surfactant C18H37(CH2CH2O)10 (C18EO10, Brij 76) under acidic hydrothermal condition. Relatively large single-phase domains were obtained in SH-SBA-12. The 3d structural solution of SHSBA-12 was obtained by Fourier analyses of HREM images. The structure is composed of spherical cavities, which are arranged in a cubic close-packed structure, in which each cavity is connected to the twelve nearestneighbor cavities through openings parallel to the 〈110〉 directions. HREM images of SBA-12 taken over large sample regions show that SBA-12 is a mixture of mostly the cubic close-packed phase, which consist of beautifully crystalline narrow bands with the same 3d structure in twin relation to each other and a relatively small amount of the 3d hexagonal close packed phase.

Mesoscale magnetism at the grain boundaries in colossal magnetoresistive films

We report the discovery of mesoscale regions with distinctive magnetic properties in epitaxial La$_{1-x}$Sr$_{x}$MnO$_{3}$ films which exhibit tunneling-like magnetoresistance across grain boundaries. By using temperature-dependent magnetic force microscopy we observe that the mesoscale regions are formed near the grain boundaries and have a different Curie temperature (up to 20 K {\it higher}) than the grain interiors. Our images provide direct evidence for previous speculations that the grain boundaries in thin films are not magnetically and electronically sharp interfaces. The size of the mesoscale regions varies with temperature and nature of the underlying defect.

Mesoscale ecohydrological modelling to analyse regional effects of climate change

Hydrological processes and crop growth were simulated for the state of Brandenburg (Germany) using the hydrological/vegetation/water quality model SWIM, which can be applied for mesoscale river basins or regions. Hydrological validation was carried out for three mesoscale river basins in the area. The crop growth module was validated regionally for winter wheat, winter barley and maize. After that the analysis of climate change impacts on hydrology and crop growth was performed, using a transient 1.5 K scenario of climate change for Brandenburg and restricting the crop spectrum to the three above mentioned crops. According to the scenario, precipitation is expected to increase. The impact study was done comparing simulation results for two scenario periods 2022–2030 and 2042–2050 with those for a reference period 1981–1992. The atmospheric CO2 concentrations for the reference period and two scenario periods were set to 346, 406 and 436 ppm, respectively. Two different methods – an empirical one and a semi-mechanistic one – were used for adjustment of net photosynthesis to altered CO2. With warming, the model simulates an increase of evapotranspiration (+9.5%, +15.4%) and runoff (+7.0%, +17.2%). The crop yield was only slightly altered under the “climate change only” scenario (no CO2 fertilization effect) for barley and maize, and it was reduced for wheat (−6.2%, −10.3%). The impact of higher atmospheric CO2 compensated for climate-related wheat yield losses, and resulted in an increased yield both for barley and maize compared to the reference scenario. The simulated combined effect of climate change and elevated CO2 on crop yield was about 7% higher for the C3 crops when the CO2 and temperature interaction was ignored. The assumption that stomatal control of transpiration is taking place at the regional scale led to further increase in crop yield, which was larger for maize than for wheat and barley. The regional water balance was practically not affected by the partial stimulation of net photosynthesis due to higher CO2, while the introduction of stomatal control of regional transpiration reduced evapotranspiration and enlarged notably runoff and ground water recharge.