ECMWF ERA-Interim Research Articles

Evaluation of WRF Model Boundary Layer Schemes in Simulating Temperature and Heat Extremes over the Middle East–North Africa (MENA) Region

Abstract We assess the sensitivity of the Weather Research and Forecasting (WRF) Model to the use of different planetary boundary layer (PBL) parameterizations focusing on air temperature and extreme heat conditions. This work aims to evaluate the performance of the WRF Model in simulating temperatures across the Middle East–North Africa (MENA) domain, explain the model biases resulting from the choice of different PBL schemes, and identify the best-performing configuration for the MENA region. Three different PBL schemes are used to downscale the ECMWF ERA-Interim climate over the MENA region at a horizontal resolution of 24 km, for the period 2000–10. These are the Mellor–Yamada–Janjić (MYJ), Yonsei University (YSU), and the asymmetric convective model, version 2 (ACM2). For the evaluation of the WRF runs, we used related meteorological variables from the ERA5 reanalysis, including summer maximum and minimum 2-m air temperature and heat extreme indices. Our results indicate that simulations tend to overestimate maximum temperatures and underestimate minimum temperatures, and we find that model errors are very dependent on the geographic location. The possible physical causes of model biases are investigated through the analysis of additional variables (such as boundary layer height, moisture, and heat fluxes). It is shown that differences among the PBL schemes are associated with differences in vertical mixing strength, which alters the magnitude of the entrainment of free-tropospheric air into the PBL. The YSU is found to be the best-performing scheme, and it is recommended in WRF climate simulations for the MENA region.

Spatiotemporal long-term wind and storm characteristics over the eastern Mediterranean Sea

The main objective of the present study is to provide a comprehensive analysis of wind characteristics over the eastern Mediterranean Sea using three widely used wind fields, namely ECMWF ERA-Interim, ECMWF ERA5, and NCEP/CFSR. Wind speeds from three reanalysis datasets were validated with measurements at three different locations (Antalya, Dardanelles, and Silifke). The results of several statistical investigations show that ERA5 and CFSR wind data provide reasonably better fits with measurements compared to results of ERA-Interim data, especially in higher percentiles. Long-term wind and storm characteristics, long-term variability, and long-term trends with statistical significance levels were evaluated covering the period of 1979–2018. Long-term strong wind conditions with no significant long-term trend were detected in the northern Aegean Sea, while relatively weak, short-lived, and highly variable winds were determined in the southern, northern, and eastern Levantine Basin. For five selected regions, local analyses such as storm duration, and 99th percentile wind speed were evaluated in detail. Extreme wind analyses indicate that the largest discrepancy between the results of ERA5 and CFSR wind datasets was observed in the eastern Levantine basin, with the RC (relative difference) exceeding 22%. The highest extreme wind speeds for the 100-year return period were found in the northern Aegean Sea with values exceeding 21 m/s and 25 m/s for ERA5 and CFSR, respectively.

The Observed Impact of the South Asian Summer Monsoon on Land-Atmosphere Heat Transfers and Its Inhomogeneity over the Tibetan Plateau

To promote Tibetan meteorological research, the third Tibetan Plateau (TP) Experiment for atmospheric sciences (TIPEX III) has been carried out over the plateau region since 2014, with near-surface heat fluxes measured at different sites. Using the observational data of near-surface heat fluxes measured at 8 plateau stations in TIPEX III, as well as the ECMWF ERA Interim reanalysis data, the land-atmosphere heat transfers over different regions of TP and their responses to the South Asian summer monsoon (SASM) during active/break periods were investigated. Inhomogeneity was found in the land-atmosphere heat transfers over the plateau, with large differences among plateau stations. During the observation period, the daily averaged total heat transfer (the sum of sensible and latent heat flux) varied from 70.2 to 101.2 Wm−2 among the 8 plateau stations, with the sensible heat flux from 18.8 to 60.1 Wm−2 and the latent heat flux from 10.1 to 74.7 Wm−2. These heat transfers were strongly affected by the SASM evolution, but with strong inhomogeneities over the plateau stations. Overall, the more southern station locations exhibited more SASM impacts. The land-atmosphere heat transfers (the total, sensible and latent heat fluxes) were greatly weakened/strengthened during the SASM active/break period at Namco (southeast plateau), Baingoin (central plateau), Lhari (central plateau), and Nagqu (central plateau), which were closely related to the weakened/strengthened radiation conditions. However, the SASM impacts were quite small or even negligible for the other plateau stations, which complicated our conclusions, and further investigations are still needed.

Development of a hybrid wind field for modeling the tropical cyclone wave field

Due to the increasing trend of tropical cyclone occurrence in the recent decades, the necessity of developing models for forecasting and hindcasting these atmospheric-oceanic hazards, becomes more apparent. One of the uncertainties about the tropical cyclones is the wind field accuracy of modeling oceanic waves and flows. In this paper, six different wind fields have been examined for hindcasting the wave field of cyclone Gonu within the areas of the Arabian Sea and the Gulf of Oman. The wind field of ECMWF (ERA-Interim) and Climate Forecast System Reanalysis (CFSR) data, that obtained via weather research forecasting (WRF) mesoscale modeling and three wind fields achieved via Holland, Rankin, Young and Sobey (S&Y) parametric models have been investigated as well. The wave field modeling results have been compared with the third-generation SWAN model in two stations within the area of Chabahar Bay. The wind field results obtained via the reanalysis models and WRF one indicate an appropriate estimation of the wave characteristics and the maximum wave height at the measurement stations. In order to better evaluate the results of different wind fields, the maximum wave height maps have been studied in the simulation time period. The results indicated that the maximum wave height values obtained from the reanalysis data do not match the track and development direction of the cyclone Gonu. The mismatch between storm development track and maximum wave height in WRF data can also be observed. The maximum significant wave height obtained via the parametric wind fields is very compatible with the cyclone Gonu track. Examining the maximum wave heights obtained via different wind fields, along with comparing the wave characteristics at the measurement stations, highlights the effect of different wind fields in hindcasting the wave characteristics, especially on the northern coasts of the Gulf of Oman. Examination of the maximum wave heights obtained from different wind fields has been investigated in this study along with comparison of wave characteristics at measurement stations. Results indicated that the optimal approach for simulating the tropical cyclone's wave field is to use a hybrid one. Therefore, a hybrid wind field has been developed which includes the wind characteristics of the parametric model in the areas near the storm source and the WRF meso scale model in the outer zone. The hybrid wind field has led to an improvement in the characteristics of waves within deep and coastal waters.

Metrics of the Hadley circulation strength and associated circulation trends

Abstract. This study compares trends in the Hadley cell (HC) strength using different metrics applied to the ECMWF ERA5 and ERA-Interim reanalyses for the period 1979–2018. The HC strength is commonly evaluated by metrics derived from the mass-weighted zonal-mean stream function in isobaric coordinates. Other metrics include the upper tropospheric velocity potential, the vertical velocity in the mid-troposphere, and the water vapour transport in the lower troposphere. Seven known metrics of HC strength are complemented here by a metric of the spatially averaged HC strength, obtained by averaging the stream function in the latitude–pressure (φ–p) plane, and by the total energy of zonal-mean unbalanced circulation in the normal-mode function decomposition. It is shown that metrics, which rely on single-point values in the φ–p plane, produce unreliable 40-year trends in both the northern and southern HCs, especially in ERA-Interim; magnitudes and even the signs of the trends depend on the choice of the HC strength metric. The two new metrics alleviate the vertical and meridional inhomogeneities of the trends in HC strength. The unbalanced energy metric suggests a positive HC trend in both reanalyses, whereas the metric based on averaging the stream function finds a significant positive trend only in ERA5.

Performance evaluation of spectral wave model caused by ERA-Interim, ERA5, and CFSR wind fields in the Black Sea

The main objective of the present study is to evaluate the performance of the MIKE 21 SW (Spectral Wave) in a semi-closed basin (Black Sea). Wind data were obtained from ECMWF ERA-Interim, ECMWF ERA5, and NCEP CFSR. The wave model was calibrated and validated with wave measurements recorded at seven different stations along the Black Sea coastlines. In the calibration, several different physical parameters were tested to determine the optimal model settings, and the whitecapping parameter (Cds) was more influential than the bottom friction parameter (kn), wave breaking parameter (γ), and nonlinear wave-wave interactions in the prediction of the Black Sea wave properties. The wave results modeled using ERA-Interim showed less agreement with wave measurements than those obtained with ERA-5 and CFSR wind fields. Although the significant wave height and wave period modeled using ERA5 and CFSR wind fields were reasonably well matched at all measurement stations, ERA5 wind fields provided slightly better performance owing to having the largest correlation coefficient (R) and lowest statistical error measures (bias, RMSE, SI) in the Black Sea.

Improved ice content, radiation, precipitation and low-level circulation over the tropical pacific from ECMWF ERA-interim to ERA5

This study evaluates changes in simulated Pacific climate between two ECMWF re-analyses; the ERA Interim (ERAI) and the newest ERA5. Changes in the Integrated Forecasting System (IFS) and possibly sea surface temperature result in greatly reduced discrepancies in ERA5’s ice water path (IWP), radiative fluxes and precipitation relative to satellite-based observational products. IWP shows the largest percentage change, increasing by over 300% from ERAI to ERA5, due to inclusion of falling ice (snow) that impacts radiative calculation. ERAI to ERA5 changes in high-cloud fraction are generally anticorrelated as expected with outgoing longwave radiation, with ERA5 having smaller longwave discrepancies versus CERES observations compared with ERAI. Reflected shortwave discrepancies are similarly reduced from ERAI to ERA5, which appears to be due to changes in both cloud fraction and optical depth. Finally, ERA5 also reduces a longstanding precipitation excess relative to the GPCP observational product in the southern trade winds region between the Southern Pacific and intertropical convergence zones. This appears to be related to cooler prescribed sea surface temperatures, thereby reducing local moisture supply via suppressing net latent heat flux and stronger surface trade-winds. Compared with GPCP and CERES, ERA5 shows similar geographic patterns of discrepancies to ERAI in terms of precipitation and top-of-atmosphere radiation, but their magnitudes are greatly reduced in ERA5.

IMK/IAA MIPAS temperature retrieval version 8: nominal measurements

Abstract. A new global set of atmospheric temperature profiles is retrieved from recalibrated radiance spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Changes with respect to previous data versions include a new radiometric calibration considering the time dependency of the detector nonlinearity and a more robust frequency calibration scheme. Temperature is retrieved using a smoothing constraint, while tangent altitude pointing information is constrained using optimal estimation. ECMWF ERA-Interim is used as a priori temperature below 43 km. Above, a priori data are based on data from the Whole Atmosphere Community Climate Model Version 4 (WACCM4). Bias-corrected fields from specified dynamics runs, sampled at the MIPAS times and locations, are used, blended with ERA-Interim between 43 and 53 km. Horizontal variability of temperature is considered by scaling an a priori 3D temperature field in the orbit plane in a way that the horizontal structure is provided by the a priori while the vertical structure comes from the measurements. Additional microwindows with better sensitivity at higher altitudes are used. The background continuum is jointly fitted with the target parameters up to 58 km altitude. The radiance offset correction is strongly regularized towards an empirically determined vertical offset profile. In order to avoid the propagation of uncertainties of O3 and H2O a priori assumptions, the abundances of these species are retrieved jointly with temperature. The retrieval is based on HITRAN 2016 spectroscopic data, with a few amendments. Temperature-adjusted climatologies of vibrational populations of CO2 states emitting in the 15 µm region are used in the radiative transfer modeling in order to account for non-local thermodynamic equilibrium. Numerical integration in the radiative transfer model is now performed at higher accuracy. The random component of the temperature uncertainty typically varies between 0.4 and 1 K, with occasional excursions up to 1.3 K above 60 km altitude. The leading sources of the random component of the temperature error are measurement noise, gain calibration uncertainty, spectral shift, and uncertain CO2 mixing ratios. The systematic error is caused by uncertainties in spectroscopic data and line shape uncertainties. It ranges from 0.2 K at 20 km altitude for northern midlatitude summer conditions to 2.3 K at 12 km for tropical conditions. The estimated total uncertainty amounts to values between 0.6 K at 20 km for midlatitude summer conditions to 2.5 K at 12–15 km for tropical conditions. The vertical resolution varies around 3 km for altitudes below 50 km. The long-term drift encountered in the previous temperature product has been largely reduced. The consistency between high spectral resolution results from 2002 to 2004 and the reduced spectral resolution results from 2005 to 2012 has been largely improved. As expected, most pronounced temperature differences between version 8 and previous data versions are found in elevated stratopause situations. The fact that the phase of temperature waves seen by MIPAS is not locked to the wave phase found in ECMWF analyses demonstrates that our retrieval provides independent information and does not merely reproduce the prior information.

Variations of Energy Fluxes with ENSO, IOD and ISV of Indian Summer Monsoon Rainfall over the Indian Monsoon Region

Variations of energy fluxes with ENSO, IOD, and Intra-Seasonal Variability of Indian Summer Monsoon Rainfall (ISMR) over the Indian monsoon region are examined using ECMWF Era Interim reanalysis over a period of 1979–2013. The composite anomalies of radiative fluxes, viz. shortwave and longwave, latent, and sensible heat as well as precipitation and winds are analyzed for the years associated with El Niño, La Niña, positive and negative IOD phases, active, and break phases of ISMR with respect to the normal years.It is observed that, the lesser (more) precipitation over the region in the El Niño (La Niña) years is accompanied with enhanced (reduced) top of the atmosphere absorbed solar radiation and outgoing long wave radiation, as well as more (less) surface absorbed solar radiation, and surface sensible heat flux.During the positive IOD phase, enhanced convective activity and precipitation rainfall over the western Equatorial Indian Ocean, Arabian Sea, and west coast of India, with reduced rainfall over the eastern equatorial Indian ocean is accompanied with enhanced shortwave and long wave radiative fluxes over most parts of the Indian subcontinent. The conditions during the negative IOD phases are largely the opposite.

Spatiotemporal long-term trends of wind and wave climate and extreme characteristics over the Sea of Marmara

The Sea of Marmara is a typical example of enclosed seas and an inland sea bounded by land-masses in four directions, and it links the Black Sea and the Mediterranean via the Bosphorus and the Dardanelles straits. Moreover, The sea of Marmara has strategic importance with possessing marine structures such as various types of terminals, cruise terminals, and marinas, and also providing a strong economic contribution with tourism revenue. This situation brings the necessity of determining the design wind and wave parameters properly. The wind and wave characteristics and their variabilities were evaluated covering the last 40 years (1979–2018) by using two well-known wind fields, i.e., ECMWF ERA-Interim and NCEP/CFSR. Wave parameters were generated from the calibrated and validated SWAN model with ERA-Interim wind data. The spatial and temporal variability of the long-term averages and long-term trends of the wind and wave characteristics were investigated, and also extreme wave conditions were evaluated in detail. This study shows that the modeling of waves in enclosed seas is more challenging compared to open seas due to several affecting factors such as land which affect the wave fields and need high spatial resolution. The results indicate that orography and islands largely affect the wind and wave climate in the Sea of Marmara. The northern side of the Sea of Marmara is characterized by stronger wind and wave climate compared to the southern side. The annual mean values of wave height have decreasing tendencies while the annual maxima tend to increase in most parts of the Sea of Marmara. The dominant wind and wave directions are observed to be in the northeast and southwest sector and their magnitudes are controlled by the orographic features over the Marmara Region.

Cold-season atmospheric conditions associated with sudden changes in PM10 concentration over Seoul, Korea

Previous studies have intensively studied the atmospheric conditions associated with high- and low-PM10 (particulate matter < 10 μm) episodes according to air quality standards. However, the association with sudden changes in PM10 concentration has not been clearly understood. Here we defined a PM10 change of above one standard deviation as a sudden change and divided these changes into PM10-increasing days (294 days) and PM10-decreasing days (277 days). We then investigated the atmospheric conditions concerning sudden changes in PM10 in Seoul, Korea during 17 cold seasons (October to March) from 2001/2002 to 2017/2018. This study used the local and synoptic atmospheric variables obtained from ECMWF ERA-Interim and ERA5, and aerosol optical depth from MODIS/Terra. On PM10-increasing days, a high-pressure anomaly was dominant in the Korean Peninsula's upper and lower atmosphere. A southerly wind, intense atmospheric stagnation, and high aerosol optical depth over the eastern region of China may also have been responsible for the increase in PM10 regardless of the preceding concentration of PM10. On PM10-decreasing days, the prevailing atmospheric pattern was subject to the preceding concentration of PM10. From the moderate (40–80 μg m−3) to the lower concentrations, a robust and low-pressure anomaly favorable for dispersion of PM10 was dominant over the Korean Peninsula. In contrast, from the high (>80 μg m−3) to the moderate concentrations, there was no distinct pattern except for a high-pressure anomaly in the upper atmosphere. These results improve our understanding of the mechanisms behind the sudden changes in PM10 due to atmospheric conditions over East Asia.

ASSESSMENT OF LONG-TERM WIND AND WAVE TRENDS IN THE BLACK SEA

The wind and wave climate over the Black Sea were investigated by providing extensive datasets covering the last 40 years (1979-2018). Wind characteristics over the Black Sea were evaluated by using two well-known wind fields (i.e., ECMWF ERA-Interim and NCEP/CFSR). Wave simulations were generated from the MIKE 21 SW model forcing with two wind datasets. The possible effect of the long-term variability on the wind and wave characteristics over the Black Sea was discussed in the context of climate change.

Prediction of lightning activity using WRF-ELEC model: Impact of initial and boundary conditions

The impact of initial conditions in predicting lightning activity using the Weather Research and Forecasting (WRF) with the electrification (ELEC) extra package, known as WRF-ELEC model, has been investigated. The severity, frequency, and some physical and dynamical properties of lightning occurred during 11 years (2004–2014) are considered. Four thundercloud events with distinctive characteristics over the Tehran area were chosen for detailed study. The selection process was made based on the observational data received from the Iranian Meteorological Organization (IRIMO), ground-based lightning data from the World Wide Lightning Location Network (WWLLN) and satellite-based lightning data from the Lightning Imaging Sensor (LIS). The WRF-ELEC simulations initialized with the European Centre for Medium-Range Weather Forecasts-ERA Interim (ECMWF-ERA Interim), National Centers for Environmental Prediction Final Analysis (NCEP-FNL) and the NCEP operational Global Forecast System (GFS) data have been conducted to obtain the Number Of Lightning flash density (NOL) associated with each case study. The numerical simulations are compared qualitatively and quantitatively with the observations. Several statistical metrics are used in order to determine the performance of the WRF-ELEC model initialized by various IBCs (initial and boundary conditions) for lightning prediction purposes. The results show that in the most of the studied cases, there is a good agreement between the simulated time-averaged horizontal patterns of the Lightning Potential Index (LPI) obtained from the ERA-Interim-based experiments and the locations of lightning occurrence of WWLLN data as well as LIS observations. Furthermore, GFS-based simulations have a better quantitative performance in the NOL prediction than FNL and ERA-Interim-based simulations regarding the values of Standard Deviation (SD), and centered Root Mean Square Error (RMSE). The results of further statistical analysis using different metrics reveal that ERA-Interim initialization has the best performance of lightning activity prediction.

Influence of synoptic scale atmospheric circulation on the development of urban heat island in Prague and Bucharest

This study has analysed the development of the urban heat island (UHI) under various synoptic scale atmospheric circulation for two large cities – Prague in central Europe and Bucharest in south-eastern Europe, including seasonal differences and long-term changes. At the best of our knowledge, it is the first comparison between two European cities from this perspective. Analysis was conducted on the base of minimum air temperature data from pairs of urban and peri-urban stations. The average UHI intensity is 2.3 °C for Prague and 1.8 °C for Bucharest, it exceeds 4 °C in 6–10% of cases, and the highest values occur in August in both cities. The annual course of monthly mean values of UHI intensities has higher amplitude in Bucharest (1.2 °C) than Prague (0.6 °C). Synoptic scale circulation is classified according to mean sea level pressure data from ECMWF Era-Interim reanalysis using cost733class software. The results show that UHI is more intense under anticyclonic situations with southern winds in the both cities. Over 1981–2016, we found that the UHI intensity followed statistically significant increasing trend, much larger trend for Bucharest than Prague (3.3 °C vs. 1.3 °C / 100 years).

Identifying the moisture source of precipitation in the southern coasts of the Caspian Sea

This research was carried out to identify the moisture source of precipitation in the southern coasts of the Caspian Sea. To achieve this purpose, two categories of data were used. The first category was the environmental data comprising of daily precipitation of 10 meteorological stations of the southern coasts of the Caspian Sea during the period 1995–2017, equal to 8401 days. The second group was atmospheric data which included the variables of zonal (u) and meridional (v) components of wind, geopotential height (z), mean sea-level pressure (msl), and specific humidity (q) extracted from the ECMWF ERA-Interim database. The Z-score was based on and used to categorize different intensities of precipitation; days with precipitation were divided into five intensity groups: light, moderate, heavy, very heavy, and extreme precipitation. To recognize the atmospheric conditions at sea level, the combined SLP and HGT maps were plotted at 500 hPa. In addition, for identifying the moisture source, Vertically Integrated Moisture Flux Convergence (VIMFC) was used. In order to recognize the moisture source of the analysis region, the troposphere was divided into three layers of low (1000–850 hPa), middle (775–700 hPa), and upper layers (600–500 hPa) based on specific humidity. The results of the cluster analysis on the Euclidean distances of sea-level pressure in days with precipitation for each of the precipitation classes showed that the greater the high-pressure intensity on the Black Sea, the greater the flux density of the convergence of moisture due to the anticyclone movement of the system toward the south coasts of the Caspian Sea. This resulted in higher precipitation rates. The results of the analysis also illustrated that the Black Sea high pressure in the first layer played a key role in transferring moisture to the southern coasts of the Caspian Sea. The Siberian high pressure in one pattern (the first pattern) and also in combination with the Black Sea high pressure played a role in transferring moisture to the region analyzed for light precipitation phenomena. At high levels (the third layer), the Saudi Arabian high pressure played a key role in transferring moisture to the study area. The findings demonstrated that the most important source of moisture was the Caspian Sea at low levels, and at upper levels (third layer), the Red Sea, Black Sea, and Mediterranean Sea were the sources of moisture.

Cloud cover over the Tibetan Plateau and eastern China: a comparison of ERA5 and ERA-Interim with satellite observations

This study examines the progress made by reanalyses and satellite products in the estimation of cloud cover over China: the ECMWF reanalyses ERA5 and ERA-Interim, geostationary satellite observation Himawari-8 (H8) and the International Satellite Cloud Climatology Project H-series (ISCCP) product. There is great similarity in spatial patterns of cloud cover in reanalyses and satellite observations, especially between ERA5 and H8. Distinct characteristics of the seasonal evolution of cloud cover are shown over the Tibetan Plateau (TP), the southeast (SE) and northeast (NE) of China. Differences in magnitudes of cloud cover exist. Overestimations are about 10% for reanalyses and about 20% for ISCCP in compared with certain cloud cover in H8. When probable cloud (about 10%) in H8 is included in the estimation, biases reduce the most in ERA5. The cloud hit rate (CHR) and false alarm rate (FAR) in against H8 and ISCCP reveal that simulated clouds in ERA5 have been improved especially over eastern China, but with limited improvement over TP in compared with ERA-Interim. Diurnal variations of cloud cover are characterized by increases during daytime over those three regions. Amplifications of diurnal variation vary over different regions and months. Satellite observations and ERA5 indicate distinguished diurnal cycle of cloud cover over TP, while further investigation based on ERA5 reveals coherent diurnal cycle in meteorological environment. Long-term changes of cloud cover highlight decreasing trends over TP and particular during March in past decades based on ISCCP and ERA5, which require further investigation in future.

Comparisons of Diurnal Variations of Land Surface Temperatures from Numerical Weather Prediction Analyses, Infrared Satellite Estimates and In Situ Measurements

This study evaluates the diurnal cycle of Land Surface Temperature (LST) from Numerical Weather Prediction (NWP) reanalyses (ECMWF ERA5 and ERA Interim), as well as from infrared satellite estimates (ISCCP and SEVIRI/METEOSAT), with in situ measurements. Data covering a full seasonal cycle in 2010 are studied. Careful collocations and cloud filtering are applied. We first compare the reanalysis and satellite products at continental and regional scales, and then we concentrate on comparisons with the in situ observations, under a large variety of environments. SEVIRI shows better agreement with the in situ measurements than the other products, with bias often less than ±2K and correlation of 0.99. Over snow or arid surface, ISCCP tends to have more systematic errors than the other products. ERA5 agrees better to the in situ over barren land than ERA Interim, particularly at night time, thanks to the new surface model. However, over vegetated surfaces, both reanalyses tend to have higher/lower temperature at night/day time than the in situ measurements, probably related to the surface processes and its interactions with atmosphere in the NWP model.

Impact Analysis of Univariate and Multivariate Bias Correction on Rice Irrigation Water Needs in Jiangxi Province, China

Regional climate models (RCMs) provide an improved representation of climate information as compared to global climate models (GCMs). However, in climate-agricultural impact studies, accurate and interdependent local-scale climate variables are preferable, but both RCMs and GCMs are still subjected to bias. This study compares univariate bias correction (UBC) and multivariate bias correction (MBC) method to simulate rice irrigation water needs (IWNs) in Jiangxi Province, China. This research uses the daily output of Hadley Centre Global Environmental Model version 3 regional climate model (HadGEM3-RA) forced with ERAINT (ECMWF ERA Interim) data and 13 Jiangxi ground-based observations, and the observation data are reference data with 1989–2005 defined as a calibration period and 2006–2007 as a validation period. The result shows that UBC and MBC methods favorably bias-corrected all climate variables during the calibration period, but still no significant difference is noted between the two methods. However, the UBC ignores the relationship between climate variables, while MBC preserves the climate variables’ interdependence which affect subsequent analyses. In rice IWNs simulation analysis, MBC has better skill at correcting bias compare to UBC in ETo (evapotranspiration) and Peff (effective rainfall) components. Nonetheless, both methods have a low ability to correct extreme values bias. Overall, both techniques successfully reduce bias, even though they are still less effective for precipitation compared to maximum and minimum temperature, relative humidity and windspeed.

Estimation of methane emissions from wetlands and most extreme fires in Western Siberia based on MACC / CAMS and GFED data

Methane is an important greenhouse gas, and its atmospheric concentration has nearly tripled since pre-industrial times. This paper presents estimates of the strength of two primary sources of methane emissions in Western Siberia: wetlands emissions (WEs) and methane emissions from biomass burning (BBEs). The atmospheric circulation data used are from ECMWF Era-Interim, BBE – GFED (Global Fire Emissions Database) and CAMS GFAS (Global Fire Assimilation System), WE – MACC-III greenhouse gases inversions, v10_an. We have revealed that the highest BBE in Western Siberia (summer periods of 2005, 2006, 2007, 2010, 2011, 2012, and 2013) are accompanied by blocking in the atmosphere. We have also showed that there is a lag of 3-6 days between the beginning of the blocking and the periods of maximum BBE. Features of Rossby wave dynamics and blocking highs and ridges are examined as a possible reason for the lag. It turned out that the maximum BBE is commonly observed when a blocking high (or ridge) is shifted from Western to Eastern Siberia. The GFAS data demonstrate higher BBE than GFED (except for 2010). According to GFED, the average emission for all years is only 14.2% from WEs (the maximum emission is 35% (2012), and the minimum one, 2.2% (2007) from WEs). According to GFAS, the average emission for all years is 38.1% from WEs (the maximum emission is 127,4% (2012), and the minimum one, 6.1 (2010) % from WEs).

Atmospheric Precipitation Within the Selenga River Basin and Large-Scale Atmospheric Circulation Over Eurasia in July

Data from the Global Precipitation Climatology Centre (GPCC) were used in investigating long-term variability of anomalies of the total amount of atmospheric precipitation within the Selenga river basin in July. We identified several long periods (four years and longer) with negative precipitation anomalies: 1935–1939, 1955–1958, 1977–1981, 2007–2011, and 2013–2017. The last period is characterized by the smallest precipitation amount. Day-to-day variations in total precipitation were also analyzed for each July from 1982 to 2016. The analysis revealed a tendency to a decrease of the number of days with a large precipitation amount and to an increase of dry periods. Based on ECMWF Era Interim data, we examined the features in the atmospheric blocking Europe, Siberia and the Far East for periods with large and small precipitation amounts within the Selenga river basin. To identify the blocking in the atmosphere used the southern gradient of the geopotential. It was shown that in periods with large precipitation amounts blockings occurred most frequently over Eastern Siberia and more rarely over Europe and the Far East (especially if they were accompanied by blocking over Western Siberia). Atmospheric precipitation within the Selenga basin is associated not only with blocking but also with the position of the jet stream and with dynamic blocking formation schemes. The significance of these factors has been demonstrated in a number of specific situations of the atmospheric circulation in years with large and small precipitation amounts within the Selenga basin. Long-term transformations of these characteristics caused by climate change and the general atmospheric circulation can lead to a disturbance of the correlations between blocking and precipitation amounts within the river basin. In all likelihood, the correlation of blocking with precipitation regimes, rather than with precipitation in the region, will be more rigid. A functional dependence of the Selenga flow on climate change appears to be determined by the position of the monsoon front and by the wave properties of atmospheric flows in midlatitudes.