Atmospheric sciences

This work analyses optical properties of the dry tropospheric aerosol measured at the regional Global Atmosphere Watch (GAW) observation site Melpitz in East Germany. For a continuous observation period between 2007 and 2010, we provide representative values of the dry-state scattering coefficient, hemispheric backscattering coefficient, absorption coefficient, single scattering albedo, and scattering Ångström exponent. Besides the direct measurement, the aerosol scattering coefficient was alternatively computed from experimental particle number size distributions using a Mie model. Within pre-defined limits, a closure could be achieved with the direct measurement. The achievement of closure implies that such calculations can be used as a high-level quality control measure for data sets involving multiple instrumentation. <br><br> All dry-state optical properties show pronounced annual and diurnal variations, which are attributed to the corresponding variations in the re...

The subseasonal-to-seasonal (S2S) predictive timescale, encompassing lead times ranging from 2 weeks to a season, is at the frontier of forecasting science. Forecasts on this timescale provide opportunities for enhanced application-focused capabilities to complement existing weather and climate services and products. There is, however, a ‘knowledge-value’ gap, where a lack of evidence and awareness of the potential socio-economic benefits of S2S forecasts limits their wider uptake. To address this gap, here we present the first global community effort at summarizing relevant applications of S2S forecasts to guide further decision-making and support the continued development of S2S forecasts and related services. Focusing on 12 sectoral case studies spanning public health, agriculture, water resource management, renewable energy and utilities, and emergency management and response, we draw on recent advancements to explore their application and utility. These case studies mark a sign...

The minimum length scale to investigate quasigeostrophic (QG) vertical motion within a mesoscale operational model is determined using simulations of 28 baroclinic systems from the North American Mesoscale Forecast System (NAM) model. Two upscaling methods are tested to find the optimal QG characteristic length. The box method takes an average of each field before performing finite-differencing calculations. The cross method samples the data at increasing distances between finite-difference calculations. The traditional QG omega equation is evaluated with each upscaling technique and found to be reliable between 800 and 200 hPa. The minimum QG length scale is found to be L = 140 km considering correlations of QG omega back to operational model values, which are [Formula: see text] for both methods on an “extended” QG omega. The box method performs marginally better than the cross method due to a larger reduction of QG forcing in higher-order wavenumbers, but at the appropriate lengt...

The authors establish the effect of urbanization on precipitation in the Pearl River Delta of China with data from an annual land use map (1988–96) derived from Landsat images and monthly climate data from 16 local meteorological stations. A statistical analysis of the relationship between climate and urban land use in concentric buffers around the stations indicates that there is a causal relationship from temporal and spatial patterns of urbanization to temporal and spatial patterns of precipitation during the dry season. Results suggest an urban precipitation deficit in which urbanization reduces local precipitation. This reduction may be caused by changes in surface hydrology that extend beyond the urban heat island effect and energy-related aerosol emissions.

During the summer of 2004 a network of 11 wind profiling radars (WPRs) was deployed in New England as part of the New England Air Quality Study (NEAQS). Observations from this dataset are used to determine their impact on numerical weather prediction (NWP) model skill at simulating coastal and offshore winds through data-denial experiments. This study is a part of the Position of Offshore Wind Energy Resources (POWER) experiment, a Department of Energy (DOE) sponsored project that uses National Oceanic and Atmospheric Administration (NOAA) models for two 1-week periods to measure the impact of the assimilation of observations from 11 inland WPRs. Model simulations with and without assimilation of the WPR data are compared at the locations of the inland WPRs, as well as against observations from an additional WPR and a high-resolution Doppler lidar (HRDL) located on board the Research Vessel Ronald H. Brown (RHB), which cruised the Gulf of Maine during the NEAQS experiment. Model eva...

The temporal evolution of nine daily precipitation indices over the northeastern Iberian Peninsula was analysed for the period 1955–2006, using data from 217 observatories. Cross-tabulation analysis enabled detection of statistically significant overlap among spatial distributions of trends in the study area. There was a general decrease in annual precipitation at most observatories, a decrease in the number of rainy days and precipitation intensity and an increase in the duration of dry spells. The frequency and contribution to annual precipitation of moderate and heavy rainfall events did not change at most observatories, or showed a decreasing trend in these events. There was very large spatial and seasonal variability, with implications for water management and risk assessment in the region. The decrease in precipitation was very marked in headwaters during winter and spring, potentially affecting reservoir management in the region. Heavy rainfall events generally decreased in the west of the region in winter, and in the east of the region in autumn, when these areas are more exposed to hazards related to extreme rainfall. Large differences in the sign and magnitude of trends occurred over very short distances, suggesting the need for dense networks of observatories to ensure reliable and robust detection of regional trends. Copyright © 2009 Royal Meteorological Society

Two existing mass-consistent models, COMPLEX and NOABL, were tested in three regions in the UK: Devon, the Northern Pennines and Shetland. In order to solve problems arising with both models, a number of modifications were made, leading to the development of a new model, MC-3. First, the entire wind field was scaled down (or up) by a certain percentage to make the wind predictions at the predictor stations as close to the observed values as possible. Second, modifications to the non-divergent process used in COMPLEX were made. Site roughness-length and anemometer height corrections were also made. The new model worked well in terms of mean wind speed predictions, and gave a significant improvement over the predictions of COMPLEX and NOABL.

All the storms and depressions that formed in the Bay of Bengal during 1974–99 have been analysed. The number of occurrences in July is not in harmony with that of other months of the monsoon. Regions stricken are taken into account on a monthly, seasonal and annual basis. The Indian coast faces almost an equal number of storms and depressions that are formed from June to November. The most vulnerable months for storms are May, October and November for Bangladesh; May for Myanmar; June, August and September for Kolkata–Vishakhapatnam in India and October and November for Vishakhapatnam–Tamilnadu in India. Most of the monsoon depressions cross the Kolkata–Vishakhapatnam coast of India. The frequency of formation has been observed to decrease during the period of analysis. It is also observed that the frequency distribution of the Bay of Bengal storms has two peaks: one in the month of May and the other in the month of November. Copyright © 2003 Royal Meteorological Society

A procedure for validating landslide susceptibility maps wasapplied in a study area in northern Spain and the results obtained compared. Validationwas used to carry out sensitivity analysis for individual variables and combinationsof variables. The validity of different map-making methods was tested, as well as theutility of different types of Favourability Functions. The results obtained show thatvalidation is essential to determine the predictive value of susceptibility maps. Italso helps to better select the most suitable function and significant variables, thus improving the efficiency of the mapping process. Validation based on a temporal strategy makes it possible to derive hazard maps from susceptibility maps.

The cross-comparison of different techniques for atmospheric integrated water vapour (IWV) measurements is the essential part of their quality assessment protocol. We inter-compare the synchronised data sets of IWV values measured by Fourier-transform infrared spectrometer Bruker 125 HR (FTIR), microwave radiometer RPG-HATPRO (MW) and global navigation satellite system receiver Novatel ProPak-V3 (GPS) at St. Petersburg site between August 2014 and October 2016. Generally, all three techniques agree well with each other and therefore are suitable for monitoring IWV values at St. Petersburg site. We show that GPS and MW data quality depends on the atmospheric conditions; in dry atmosphere (IWV smaller than 6 mm), these techniques are less reliable at St. Petersburg site than the FTIR method. We evaluate the upper bound of statistical measurement errors for clear-sky conditions as 0.33 ± 0.03 mm (2.0 ± 0.3 %), 0.54 ± 0.03&t...

El estudio se realizó en la ciudad de Pinar del Río en Cuba durante el período 2006-2010, donde se analizó el comportamiento de la estabilidad atmosférica y altura de la capa de mezcla. Para obtener la categoría de estabilidad atmosférica se utilizó la clasificación de acuerdo a la longitud de Monin-Obukhov. La metodología para calcular la altura la capa de mezcla, estuvo basada en el procedimiento establecido en el preprocesador meteorológico AERMET, con algunas modificaciones por no disponer sondeos de aire superior. Además se caracterizaron los comportamientos de la estabilidad atmosférica y altura de la capa de mezcla en los diversos Tipos de Situaciones Sinópticas (TSS). Finalmente se muestran la variación horaria y mensual de la estabilidad atmosférica y de la altura de la capa de mezcla, así como la variación mensual a las 7, 13, 16 y 17 horas. Se pudo determinar que las mejores condiciones para la dispersión y el mezclamiento de los contaminantes en la atmósfera ocurren en l...

We present a new seasonal forecasting model for the June-September rains in Ethiopia. It has previously been found that the total June-September rainfall over the whole country is difficult to predict using statistical methods. A detailed study of all available data shows the rainfall seasonality varies greatly from one region to another, which would explain why the total June-September rainfall over all regions is a difficult property to forecast. In addition, the correlation between rainfall and the southern oscillation index varies spatially, with a strong teleconnection present only in some regions. This study accounts for the spatial variability in rainfall by grouping the rain gauge stations into four geographical clusters based on seasonality and cross-correlation of rainfall anomalies. Linear regression equations are then developed separately for each cluster. The variables we use for the regressions are sea-surface temperature anomalies in the preceding March, April and May of the tropical western Indian Ocean, the tropical eastern Indian Ocean, and Niño3.4. Formal skill testing of the equations shows that the new forecasting scheme is more effective in central western Ethiopia than either climatology or persistence - the methods currently used by the Ethiopian National Meteorological Services Agency.

Field observations and quantum chemical calculations have shown that organic amine compounds may be important in new particle formation processes involving H2SO4. Here, we report laboratory observations that investigate the effect of trimethylamine (TMA) on H2SO4-H2O nucleation made under aerosol precursor concentrations typically found in the lower troposphere ([H2SO4] of 106-107 cm-3; [TMA] of 180-1350 pptv). These results show that the threshold [H2SO4] needed to produce the unity nucleation rate ([H2SO4] of 106-107 cm-3) and the number of precursor molecules in the critical cluster (nH2SO4 = 4-6; nTMA = 1) are surprisingly similar to those found in the ammonia (NH3) ternary nucleation study (Benson et al., 2010a). At lower RH, however, enhancement in nucleation rates due to TMA was up to an order of magnitude greater than that due to NH3. These findings imply that both amines and NH3 are important nucleation species, but under dry atmospheric conditions, amines may have stronger effects on H2SO4 nucleation than NH3. Aerosol models should therefore take into account inorganic and organic bases together to fully understand the widespread new particle formation events in the lower troposphere.