Spatial verification approaches as a tool to evaluate the performance of high resolution precipitation forecasts

The spatial resolution of Numerical Weather Prediction (NWP) models has increased significantly in recent years. While high-resolution models are able to produce more detailed precipitation structures, their true benefit lies in more realistic statistics rather than the information provided for a specific grid point. Unfortunately, NWP model verification using traditional grid-point-by-grid-point methods has not managed to keep pace due to the limited amount of point observations available in comparable resolution. Spatial verification methods represent a possible solution since they reward closeness or resemblance by relaxing the requirement for exact matches between the forecast and observations. An intense convective event in the Mediterranean region is used as a test case to analyze the forecasting performance of the Consortium for Small-scale Modeling model (COSMO) at two different resolutions. Satellite estimates of precipitation are used as ground truth. The precipitation forecasts are assessed using various spatial methods and averaging techniques, each of which provides distinctly useful information on model performance. The results from this particular test case indicate that a neighbourhood verification framework as well as the use of the Structure, Amplitude and Location (SAL) index, which belongs to the object-based methods, can identify the scales and precipitation thresholds at which the fine resolution configuration (COSMO-GR3) provides more accurate forecasts than the coarser resolution configuration (COSMO-GR7) and is therefore worth the additional computational burden. Additional insight is gained by comparing the results of various spatial methods with traditional verification metrics based on point observations. Finally, it is demonstrated that the interpolation method used in the adaptation of data at various scales can, in some cases, influence verification results as much as model resolution. © 2017 Elsevier B.V

Developing gridded climate data sets of precipitation for Greece based on homogenized time series

The creation of realistic gridded precipitation fields improves our understanding of the observed climate and is necessary for validating climate model output for a wide range of applications. The challenge in trying to represent the highly variable nature of precipitation is to overcome the lack of density of observations in both time and space. Data sets of mean monthly and annual precipitations were developed for Greece in gridded format with an analysis of 30 arcsec (~800 m) based on data from 1971 to 2000. One hundred and fifty-seven surface stations from two different observation networks were used to cover a satisfactory range of elevations. Station data were homogenized and subjected to quality control to represent changes in meteorological conditions rather than changes in the conditions under which the observations were made. The Meteorological Interpolation based on Surface Homogenized Data Basis (MISH) interpolation method was used to develop data sets that reproduce, as closely as possible, the spatial climate patterns over the region of interest. The main geophysical factors considered for the interpolation of mean monthly precipitation fields were elevation, latitude, incoming solar irradiance, Euclidian distance from the coastline, and land-to-sea percentage. Low precipitation interpolation uncertainties estimated with the cross-validation method provided confidence in the interpolation method. The resulting high-resolution maps give an overall realistic representation of precipitation, especially in fall and winter, with a clear longitudinal dependence on precipitation decreasing from western to eastern continental Greece. © 2019 by the authors

Identifying the Skill of Higher Resolution Precipitation Forecasts with Neighborhood Verification Techniques

As numerical weather prediction models began to increase considerably in resolution, it became clear that traditional grid-point-by-grid-point verification methods did not provide material information about forecast performance. High-resolution numerical weather prediction (NWP) models produce more detailed precipitation structures but the real benefit is the more realistic statistics obtained from the higher resolution rather than the information for the specific grid point. Neighborhood verification rewards closeness by relaxing the requirement for exact matches between forecasts and observations. The advantage of the neighborhood approachis the use of a spatialwindowsurrounding the forecast and/or observedpoints. The size of the neighborhood can be varied to provide verification results at multiple scales, enabling the determination of which scales the forecast has the most useful skill. A strong convective event is used as a test case for forecasting precipitation over the complexterrain of the Alps. Theavailable precipitation data are treated withinwindows using a variety of methods for averaging (upscaling), thresholding, and PDF generation, each of which provides distinctly useful information on model performance

Numerical Modeling Analysis of Tornadoes Using the COSMO.GR Model Over Greece

The COnsortium for Small-scale MOdeling (COSMO) was formed in October 1998, and its general goal is to develop, improve and maintain a non-hydrostatic limited-area atmospheric model, while the Hellenic National Meteorological Service joined the consortium in 1999. The COSMO model has been designed both for operational numerical weather prediction (NWP) as well as various scientific applications on the meso-beta and meso-c scale. Two tornado case studies were selected to investigate the ability of COSMO model to depict the characteristics of severe convective weather, which favored the development of the associated storms. The first tornado occurred, close to Ag. Ilias village, 8 km northwestern from Aitoliko city over western Greece on February 7, 2013, while the second tornado developed close to Palio Katramio village, 8 km southern from Xanthi city over northern Greece on November 25, 2015. Although both tornadoes had a short lifetime, they caused significant impacts. The COSMO. GR atmospheric model was initialized with analysis boundary conditions obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF). The resulting numerical products with spatial resolution of 0.020 degrees (similar to 2 km) over the geographical domain of Greece depicted very well the severe convective conditions close to tornadoes formation

Assessment of offshore wind power potential in the Aegean and Ionian Seas based on high-resolution hindcast model results

In this study long-term wind data obtained from high-resolution hindcast simulations is used to analytically assess offshore wind power potential in the Aegean and Ionian Seas and provide wind climate and wind power potential characteristics at selected locations, where offshore wind farms are at the concept/planning phase. After ensuring the good model performance through detailed validation against buoy measurements, offshore wind speed and wind direction at 10 m above sea level are statistically analyzed on the annual and seasonal time scale. The spatial distribution of the mean wind speed and wind direction are provided in the appropriate time scales, along with the mean annual and the inter-annual variability; these statistical quantities are useful in the offshore wind energy sector as regards the preliminary identification of favorable sites for exploitation of offshore wind energy. Moreover, the offshore wind power potential and its variability are also estimated at 80 m height above sea level. The obtained results reveal that there are specific areas in the central and the eastern Aegean Sea that combine intense annual winds with low variability; the annual offshore wind power potential in these areas reach values close to 900 W/m2, suggesting that a detailed assessment of offshore wind energy would be worth noticing and could lead in attractive investments. Furthermore, as a rough estimate of the availability factor, the equiprobable contours of the event [4 m/s ≤ wind speed ≤ 25 m/s] are also estimated and presented. The selected lower and upper bounds of wind speed correspond to typical cut-in and cut-out wind speed thresholds, respectively, for commercial offshore wind turbines. Finally, for seven offshore wind farms that are at the concept/planning phase the main wind climate and wind power density characteristics are also provided. © 2017 Takvor Soukissian, et al

Indoor air quality assessment in an underground parking facility

This paper presents an indoor air quality (IAQ) assessment in a representative underground parking facility (UPF) using carbon monoxide and volatile organic compounds as IAQ indicators. For this purpose, concentrations of both pollutants were measured at different time intervals throughout the day. Vehicular emission factors (EFs) were estimated using the EMFAC7F1.1 model. A transient mass balance model was then applied to construct concentration profiles. The ventilation rates required to maintain pollutant concentrations within acceptable standards were estimated under maximum UPF occupancy, and a sensitivity analysis was conducted to evaluate the effect of changes in EMFAC7F1.1 input parameters on EFs and ventilation rates

Modeling of combined aerosol and photooxidant processes in the Mediterranean area

The combined UAM-AERO/RAMS modeling system has been applied to study the dynamics of photochemical gaseous species and particulate matter processes in the eastern Mediterranean area between the Greek mainland and the island of Crete. In particular, the modeling system is applied to simulate atmospheric conditions for two periods, i.e., 13-16 July 2000 and 26-30 July 2000. The spatial and temporal distributions of both gaseous and particulate matter pollutants have been extensively studied together with the identification of major emission sources in the area. New pre-processors were developed for the UAM-AERO model for evaluating detailed emission inventories for biogenic compounds, resuspended dust and sea salt. Comparison of the modeling results with measured data was performed and satisfactory agreement was found for a number of gaseous species. However, the model underestimates the PM10 measured concentrations during summer. This is mainly due to the considerable underestimation of particulate matter emissions and in particular dust resuspension, the effect of forest fire emissions and the contribution of Saharan dust episodes. © 2004 Kluwer Academic Publishers

Modeling of combined aerosol and photooxidant processes in the Mediterranean area

The combined UAM-AERO/RAMS modeling system has been applied to study the dynamics of photochemical gaseous species and particulate matter processes in the eastern Mediterranean area between the Greek mainland and the island of Crete. In particular, the modeling system is applied to simulate atmospheric conditions for two periods, i.e., 13-16 July 2000 and 26-30 July 2000. The spatial and temporal distributions of both gaseous and particulate matter pollutants have been extensively studied together with the identification of major emission sources in the area. New pre-processors were developed for the UAM-AERO model for evaluating detailed emission inventories for biogenic compounds, resuspended dust and sea salt. Comparison of the modeling results with measured data was performed and satisfactory agreement was found for a number of gaseous species. However, the model underestimates the PM10 measured concentrations during summer. This is mainly due to the considerable underestimation of particulate matter emissions and in particular dust resuspension, the effect of forest fire emissions and the contribution of Saharan dust episodes. © 2004 Kluwer Academic Publishers