scholarly journals Characteristics of convective snow bands along the Swedish east coast

2017 ◽  
Vol 8 (1) ◽  
pp. 163-175 ◽  
Author(s):  
Julia Jeworrek ◽  
Lichuan Wu ◽  
Christian Dieterich ◽  
Anna Rutgersson
Keyword(s):  
Regional Climate Model ◽  
East Coast ◽  
Climate Model ◽  
Regional Climate ◽  
Open Water ◽  
Atmospheric Model ◽  
Ocean Model ◽  
Sea Surface ◽  
Precipitation Rate ◽  
Shallow Convection

Abstract. Convective snow bands develop in response to a cold air outbreak from the continent or the frozen sea over the open water surface of lakes or seas. The comparatively warm water body triggers shallow convection due to increased heat and moisture fluxes. Strong winds can align with this convection into wind-parallel cloud bands, which appear stationary as the wind direction remains consistent for the time period of the snow band event, delivering enduring snow precipitation at the approaching coast. The statistical analysis of a dataset from an 11-year high-resolution atmospheric regional climate model (RCA4) indicated 4 to 7 days a year of moderate to highly favourable conditions for the development of convective snow bands in the Baltic Sea region. The heaviest and most frequent lake effect snow was affecting the regions of Gävle and Västervik (along the Swedish east coast) as well as Gdansk (along the Polish coast). However, the hourly precipitation rate is often higher in Gävle than in the Västervik region. Two case studies comparing five different RCA4 model setups have shown that the Rossby Centre atmospheric regional climate model RCA4 provides a superior representation of the sea surface with more accurate sea surface temperature (SST) values when coupled to the ice–ocean model NEMO as opposed to the forcing by the ERA-40 reanalysis data. The refinement of the resolution of the atmospheric model component leads, especially in the horizontal direction, to significant improvement in the representation of the mesoscale circulation process as well as the local precipitation rate and area by the model.

scholarly journals Characteristics of Convective Snow Bands in the Baltic Sea Area

2016 ◽  
Author(s):  
Julia Jeworrek ◽  
Lichuan Wu ◽  
Christian Dieterich ◽  
Anna Rutgersson
Keyword(s):  
Baltic Sea ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Open Water ◽  
Ocean Model ◽  
Precipitation Rate ◽  
Shallow Convection ◽  
The Baltic Sea ◽  
The Baltic

Abstract. Convective snow bands develop in response to a cold air outbreak from the continent over the open water surface of lakes or seas. The comparatively warm water body triggers shallow convection due to increased heat and moisture fluxes. Strong winds can align with this convection into wind-parallel cloud bands, which appear stationary as the wind direction remains consistent for the time period of the snow band event, delivering enduring snow precipitation at the approaching coast. The statistical analysis of a dataset from an 11-year high resolution atmospheric regional climate model (RCA4) indicated 4 to 7 days a year of moderate to highly favorable conditions for the development of convective snow bands in the Baltic Sea region. The heaviest and most frequent lake effect snow was affecting the regions of Gävle and Västervik (along the Swedish east coast) as well as Gdansk (along the Polish coast). However, the hourly precipitation rate is often higher in Gävle than in the Västervik region. Two case studies comparing five different RCA4 model setups have shown that the Rossby Centre atmospheric regional climate model RCA4 provides a superior representation of the sea surface with more accurate SST values when coupled to the ice-ocean model NEMO as opposed to the forcing by the ERA-40 reanalysis data. The refinement of the resolution of the atmospheric model component lead especially in horizontal direction to significant improvement on the representation of the mesoscale circulation process as well as the local precipitation rate and area by the model.

scholarly journals Evaluating the representation of Australian East Coast Lows in a regional climate model ensemble

2016 ◽  
Vol 66 (2) ◽  
pp. 108-124 ◽  
Author(s):  
Alejandro Di Luca ◽  
Jason Evans ◽  
Acacia Pepler ◽  
Lisa Alexander ◽  
Daniel Argüeso
Keyword(s):  
Regional Climate Model ◽  
East Coast ◽  
Climate Model ◽  
Regional Climate ◽  
Model Ensemble

scholarly journals Internal Model Variability of the Regional Coupled System Model GCOAST-AHOI

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 227 ◽  
Author(s):  
Ha Thi Minh Ho-Hagemann ◽  
Stefan Hagemann ◽  
Sebastian Grayek ◽  
Ronny Petrik ◽  
Burkhardt Rockel ◽  
...  
Keyword(s):  
Internal Model ◽  
Climate Model ◽  
Extreme Event ◽  
Regional Climate ◽  
Coupled System ◽  
Internal Variability ◽  
Atmospheric Model ◽  
Ocean Model ◽  
System Model ◽  
Model Variability

Simulations of a Regional Climate Model (RCM) driven by identical lateral boundary conditions but initialized at different times exhibit the phenomenon of so-called internal model variability (or in short, Internal Variability—IV), which is defined as the inter-member spread between members in an ensemble of simulations. Our study investigates the effects of air-sea coupling on IV of the regional atmospheric model COSMO-CLM (CCLM) of the new regional coupled system model GCOAST-AHOI (Geesthacht Coupled cOAstal model SysTem: Atmosphere, Hydrology, Ocean and Sea Ice). We specifically address physical processes parameterized in CCLM, which may cause a large IV during an extreme event, and where this IV is affected by the air-sea coupling. Two six-member ensemble simulations were conducted with GCOAST-AHOI and the stand-alone CCLM (CCLM_ctr) for a period of 1 September–31 December 2013 over Europe. IV is expressed by spreads within the two sets of ensembles. Analyses focus on specific events during this period, especially on the storm Christian occurring from 27 to 29 October 2013 in northern Europe. Results show that simulations of CCLM_ctr vary largely amongst ensemble members during the storm. By analyzing two members of CCLM_ctr with opposite behaviors, we found that the large uncertainty in CCLM_ctr is caused by a combination of two factors (1) uncertainty in parameterization of cloud-radiation interaction in the atmospheric model. and (2) lack of an active two-way air-sea interaction. When CCLM is two-way coupled with the ocean model, the ensemble means of GCOAST-AHOI and CCLM_ctr are relatively similar, but the spread is reduced remarkably in GCOAST-AHOI, not only over the ocean where the coupling is done but also over land due to the land-sea interactions.

scholarly journals New lessons on the Sudd hydrology learned from remote sensing and climate modeling

2006 ◽  
Vol 10 (4) ◽  
pp. 507-518 ◽  
Author(s):  
Y. A. Mohamed ◽  
H. H. G. Savenije ◽  
W. G. M. Bastiaanssen ◽  
B. J .J. M. van den Hurk
Keyword(s):  
Remote Sensing ◽  
Regional Climate Model ◽  
Land Surface ◽  
Evaporation Rate ◽  
Climate Model ◽  
Regional Climate ◽  
Remote Sensing Data ◽  
Open Water ◽  
Groundwater Table ◽  
Water Evaporation

Abstract. Despite its local and regional importance, hydro-meteorological data on the Sudd (one of Africa's largest wetlands) is very scanty. This is due to the physical and political situation of this area of Sudan. The areal size of the wetland, the evaporation rate, and the influence on the micro and meso climate are still unresolved questions of the Sudd hydrology. The evaporation flux from the Sudd wetland has been estimated using thermal infrared remote sensing data and a parameterization of the surface energy balance (SEBAL model). It is concluded that the actual spatially averaged evaporation from the Sudd wetland over 3 years of different hydrometeorological characteristics varies between 1460 and 1935 mm/yr. This is substantially less than open water evaporation. The wetland area appears to be 70% larger than previously assumed when the Sudd was considered as an open water body. The temporal analysis of the Sudd evaporation demonstrated that the variation of the atmospheric demand in combination with the inter-annual fluctuation of the groundwater table results into a quasi-constant evaporation rate in the Sudd, while open water evaporation depicts a clear seasonal variability. The groundwater table characterizes a distinct seasonality, confirming that substantial parts of the Sudd are seasonal swamps. The new set of spatially distributed evaporation parameters from remote sensing form an important dataset for calibrating a regional climate model enclosing the Nile Basin. The Regional Atmospheric Climate Model (RACMO) provides an insight not only into the temporal evolution of the hydro-climatological parameters, but also into the land surface climate interactions and embedded feedbacks. The impact of the flooding of the Sudd on the Nile hydroclimatology has been analysed by simulating two land surface scenarios (with and without the Sudd wetland). The paper presents some of the model results addressing the Sudd's influence on rainfall, evaporation and runoff of the river Nile, as well as the influence on the microclimate. The paper presents a case study that confirms the feasibility of using remote sensing data (with good spatial and poor temporal coverage) in conjunction with a regional climate model. The combined model provides good temporal and spatial representation in a region characterized by extremely scarce ground data.

Investigating marine heat waves with a coupled atmosphere-ocean regional climate model

2021 ◽  
Author(s):  
Marie Pontoppidan ◽  
Priscilla Mooney ◽  
Jerry Tjiputra
Keyword(s):  
Climate Model ◽  
Heat Waves ◽  
Human Life ◽  
Regional Climate ◽  
Atmospheric Model ◽  
Ocean Model ◽  
Environmental Drivers ◽  
Climate Simulation ◽  
Substantial Impact ◽  
Spatio Temporal

<p>Marine heat waves (MHW’s) exert a substantial impact on human life and ecosystems in the ocean. In the western part of the tropical Atlantic basin, coral reefs are impacted by such events, resulting in coral bleaching and subsequently loss of biodiversity. To mitigate future changes in MHW’s it is detrimental to increase our mechanistic understanding of these events, and this must be investigated on a local scale to understand the smaller scale driving processes of the heat waves, e.g. air-sea interactions, and the spatio-temporal extent on environmental drivers essential for the ecosystem processes.</p><p>Here we use a coupled ocean-atmosphere modelling system (COAWST), which includes the atmospheric model WRF and the ocean model ROMS (including the Fennel ecosystem module), to dynamically downscale an area consisting of the Caribbean Sea and the Gulf of Mexico. Our 12 km grid spacing resolves (at least partly) smaller scale phenomena and in combination with the coupling of the ocean and the atmospheric model, it ensures a skilled representation of the air-sea interactions which are important for MHW’s. We will show the results of this decadal climate simulation with regards to generation, evolution and persistence of the MHW’s.</p>

scholarly journals The COSMO-CLM 4.8 regional climate model coupled to regional ocean, land surface and global earth system models using OASIS3-MCT: description and performance

2017 ◽  
Vol 10 (4) ◽  
pp. 1549-1586 ◽  
Author(s):  
Andreas Will ◽  
Naveed Akhtar ◽  
Jennifer Brauch ◽  
Marcus Breil ◽  
Edouard Davin ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Direct Cost ◽  
Land Surface ◽  
Climate Model ◽  
Regional Climate ◽  
Ocean Model ◽  
Earth System ◽  
Climate System Model ◽  
Community Land Model ◽  
Computational Performance

Abstract. We developed a coupled regional climate system model based on the CCLM regional climate model. Within this model system, using OASIS3-MCT as a coupler, CCLM can be coupled to two land surface models (the Community Land Model (CLM) and VEG3D), the NEMO-MED12 regional ocean model for the Mediterranean Sea, two ocean models for the North and Baltic seas (NEMO-NORDIC and TRIMNP+CICE) and the MPI-ESM Earth system model.We first present the different model components and the unified OASIS3-MCT interface which handles all couplings in a consistent way, minimising the model source code modifications and defining the physical and numerical aspects of the couplings. We also address specific coupling issues like the handling of different domains, multiple usage of the MCT library and exchange of 3-D fields.We analyse and compare the computational performance of the different couplings based on real-case simulations over Europe. The usage of the LUCIA tool implemented in OASIS3-MCT enables the quantification of the contributions of the coupled components to the overall coupling cost. These individual contributions are (1) cost of the model(s) coupled, (2) direct cost of coupling including horizontal interpolation and communication between the components, (3) load imbalance, (4) cost of different usage of processors by CCLM in coupled and stand-alone mode and (5) residual cost including i.a. CCLM additional computations.Finally a procedure for finding an optimum processor configuration for each of the couplings was developed considering the time to solution, computing cost and parallel efficiency of the simulation. The optimum configurations are presented for sequential, concurrent and mixed (sequential+concurrent) coupling layouts. The procedure applied can be regarded as independent of the specific coupling layout and coupling details.We found that the direct cost of coupling, i.e. communications and horizontal interpolation, in OASIS3-MCT remains below 7 % of the CCLM stand-alone cost for all couplings investigated. This is in particular true for the exchange of 450 2-D fields between CCLM and MPI-ESM. We identified remaining limitations in the coupling strategies and discuss possible future improvements of the computational efficiency.

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