The Open Atmospheric Science Journal最新文献

{"title":"Improving Wind and Rain Simulations for Tropical Cyclones with the Assimilation of Doppler Radar Data","authors":"T. E. Cheung, P. Chan","doi":"10.2174/1874282301004010057","DOIUrl":"https://doi.org/10.2174/1874282301004010057","url":null,"abstract":"More accurate prediction of the strong winds and heavy rain associated with tropical cyclones using numerical weather prediction (NWP) models would be helpful in the provision of weather services for the public. In this paper, the impact of assimilating radar data in the simulation of Typhoon Neoguri and Severe Tropical Storm Kammuri in 2008 is studied using Weather Research and Forecasting (WRF) version 2.2 and WRF VAR version 2.1. Only the data from the radar at Tate's Cairn in Hong Kong are considered. Four experiments are conducted, namely, (a) simulation without radar data, (b) simulation with radar data assimilated at the initial time, (c) cycling simulation with the assimilation of radar data (Doppler velocity and reflectivity) directly assimilated, and (d) cycling simulation with the assimilation of 2D wind field retrieved from the Doppler velocity data from the radar. By comparing with actual observations of the surface wind distribution in Hong Kong and the actual radar reflectivity data, it turns out that both (c) and (d) outperform (a) and (b), and (c) and (d) show comparable skills. As a result, cycling simulation with the assimilation of weather radar data (even for a single radar) could improve the prediction of winds and rain bands associated with tropical cyclones.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131276783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On The Dominance of 28-Month Harmonic in the Equatorial- Stratospheric-Wind Quasi Biennial Oscillation","authors":"A. Mazzarella, A. Giuliacci","doi":"10.2174/1874282301004010053","DOIUrl":"https://doi.org/10.2174/1874282301004010053","url":null,"abstract":"The Quasi Biennial Oscillation, the downward propagating easterly and westerly wind regimes in the equatorial stratosphere, has been investigated according to robust statistics that utilizes the amplitude/vector probable error ratio to provide the confidence level of the investigated harmonic. The amplitude-to-noise ratio is found to be the highest in correspondence of the 28- month harmonic for each examined height; the relative amplitude and phase values are found, respectively, to decrease and increase with the height and to take about a year to descend from 15 to 70 hPa with a progressive lag of about 1 month/km. At the top of the stratosphere, easterlies dominate, while at the bottom, westerlies are more likely to be found.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130984057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theoretical investigations on potential impacts of high-latitude volcanic emissions of heat, aerosols and water vapor and their interactions with clouds and precipitation.","authors":"M. B. Yarker, D. Paimazumder, C. Cahill, Jonathan Dehn, A. Prakash, N. Mölders","doi":"10.2174/1874282301004010024","DOIUrl":"https://doi.org/10.2174/1874282301004010024","url":null,"abstract":"Augustine Volcano (located in the Cook Inlet of South Central Alaska at 59.4 o N and 153.4 o W) erupted in January 2006 and released, among other things, water vapor, radiation heat, and aerosols into the atmosphere. To determine the potential impact of volcanic emissions and ashfall on local weather, 16 simulations assuming artificial emission and ashfall scenarios were performed with the Weather Research and Forecasting model for 24 consecutive days starting the day before the first eruption. These simulations include (1) the control simulation without consideration of any volcanic perturbation, (2) four simulations with simplified scenarios for each individual volcanic factor (radiative heat from the caldera, water vapor, cloud condensation nuclei (CCN) and/or ice nuclei (IN) aerosols, and albedo change due to ashfall), and (3) 11 simulations containing all possible combinations of these factors. These 11 simulations serve to examine interactions among impacts of the different perturbations under the assumed scenarios. The impact of volcanic factors on local weather depends on the synoptic situation, emission strength, (combination of) volcanic factors, and interaction among impacts of factors if they occur concurrently. ANalysis Of VAriance shows that the greatest (statistically significant at the 95% or higher confidence level) volcanic impact occurs on relatively humid days and immediately downwind of the volcano (<50 km). Depending on relative humidity and temperature conditions, volcanic heat release can increase condensation and/or cloud top levels or reduce cloudiness. Due to non-linear cloud microphysical processes, meteorological responses to volcanic factors can diminish or enhance the impacts of the individual factors when factors occur concurrently. As an example, depending on the ambient conditions, concurrently occurring volcanic factors can lead to a decrease in precipitation at one time and an increase at another time. These findings indicate that in the immediate vicinity of erupting volcanoes, predicted cloud conditions and precipitation may be inaccurate due to the unknown volcanic forcing.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130843743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correcting for Circumsolar and Near-Horizon Errors in Sky Cover Retrievals from Sky Images","authors":"C. Long","doi":"10.2174/1874282301004010045","DOIUrl":"https://doi.org/10.2174/1874282301004010045","url":null,"abstract":"Fractional sky cover amounts retrieved from sky imagery are overestimated significantly at times due to occurrences of “whitening” near the sun, and near the horizon for low sun, in the images. This phenomenon occurs due to forward scattering of visible light by aerosols and haze, and the intensity range limitations of the detectors of the cameras used to record the sky images. Our results suggest that when the problem occurs, the magnitude of the overestimate is typically on the order of about 10% to 20% fractional sky cover. To help alleviate this problem, a statistical analysis of the time series of the areas in the image near the sun position and along the horizon centered on the solar azimuth angle has been developed. This statistical analysis requires that images be captured frequently, at least once per minute. For times when the overestimation is detected as occurring, a correction is applied to the retrieved sky cover amounts. When the sky cover amount correction is applied, analysis indicates that the result better matches the actual sky conditions present, as noted by visual inspection of the sky images in question. In addition, frequency-of-occurrence histogram comparisons show that the adjusted results improve the agreementmore » with other methodologies and expectations. Thus, the methodology presented here helps produce more accurate fractional sky cover retrievals.« less","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"127 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115958184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calibration of TRMM derived rainfall over Nepal during 1998-2007.","authors":"Md. Nazrul Islam, Someshwar Das, H. Uyeda","doi":"10.2174/1874282301004010012","DOIUrl":"https://doi.org/10.2174/1874282301004010012","url":null,"abstract":"In this study rainfall is calculated from Tropical Rainfall Measuring Mission (TRMM) Version 6 (V6) 3B42 datasets and calibrated with reference to the observed daily rainfall by rain-gauge collected at 15 locations over Nepal during 1998-2007. In monthly, seasonal and annual scales TRMM estimated rainfalls follow the similar distribution of historical patterns obtained from the rain-gauge data. Rainfall is large in the Southern parts of the country, especially in the Central Nepal. Day-to-day rainfall comparison shows that TRMM derived trend is very similar to the observed data but TRMM usually underestimates rainfall on many days with some exceptions of overestimation on some days. The correlation coefficient of rainfalls between TRMM and rain-gauge data is obtained about 0.71. TRMM can measure about 65.39% of surface rainfall in Nepal. After using calibration factors obtained through regression expression the TRMM estimated rainfall over Nepal becomes about 99.91% of observed data. TRMM detection of rainy days is poor over Nepal; it can approximately detect, under-detect and over-detect by 19%, 72% and 9% of stations respectively. False alarm rate, probability of detection, threat score and skill score are calculated as 0.30, 0.68, 0.53 and 0.55 respectively. Finally, TRMM data can be utilized in measuring mountainous rainfall over Nepal but exact amount of rainfall has to be calculated with the help of adjustment factors obtained through calibration procedure. This preliminary work is the preparation of utilization of Global Precipitation Measurement (GPM) data to be commencing in 2013.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116715150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regional Model Nesting within GFS Daily Forecasts Over West Africa","authors":"L. Druyan, M. Fulakeza, P. Lonergan, R. Worrell","doi":"10.2174/1874282301004010001","DOIUrl":"https://doi.org/10.2174/1874282301004010001","url":null,"abstract":"The study uses the RM3, the regional climate model at the Center for Climate Systems Research of Columbia University and the NASA/Goddard Institute for Space Studies (CCSR/GISS). The paper evaluates 30 48-hour RM3 weather forecasts over West Africa during September 2006 made on a 0.5° grid nested within 1° Global Forecast System (GFS) global forecasts. September 2006 was the Special Observing Period #3 of the African Monsoon Multidisciplinary Analysis (AMMA). Archived GFS initial conditions and lateral boundary conditions for the simulations from the US National Weather Service, National Oceanographic and Atmospheric Administration were interpolated four times daily. Results for precipitation forecasts are validated against Tropical Rainfall Measurement Mission (TRMM) satellite estimates and data from the Famine Early Warning System (FEWS), which includes rain gauge measurements, and forecasts of circulation are compared to reanalysis 2. Performance statistics for the precipitation forecasts include bias, root-mean-square errors and spatial correlation coefficients. The nested regional model forecasts are compared to GFS forecasts to gauge whether nesting provides additional realistic information. They are also compared to RM3 simulations driven by reanalysis 2, representing \"high potential skill\" forecasts, to gauge the sensitivity of results to lateral boundary conditions. Nested RM3/GFS forecasts generate excessive moisture advection toward West Africa, which in turn causes prodigious amounts of model precipitation. This problem is corrected by empirical adjustments in the preparation of lateral boundary conditions and initial conditions. The resulting modified simulations improve on the GFS precipitation forecasts, achieving time-space correlations with TRMM of 0.77 on the first day and 0.63 on the second day. One real- time RM3/GFS precipitation forecast made at and posted by the African Centre of Meteorological Application for Development (ACMAD) in Niamey, Niger is shown.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127097800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Sting Jet in a Simulated Extratropical Cyclone","authors":"Z. Cao","doi":"10.2174/1874282300903010212","DOIUrl":"https://doi.org/10.2174/1874282300903010212","url":null,"abstract":"The sting jet (SJ), distinguished from warm and cold conveyor belt jets, has significant impacts on our society and economy through producing damaging surface winds. The purpose of this study is to confirm two scientific hypotheses on the SJ through diagnosing the idealized numerical simulation. It is confirmed that the SJ exists and produces severe surface winds in the simulated extratropical cyclone with explosively deepening and formation of the bent-back front. It is shown that strong winds in the SJ with a speed of about 30 m s -1 are first appeared in a cloud free zone. It is further demonstrated that the SJs are located at the tip of the bent-back front and the cloud head, and to the south/southwest of the surface low center. These features are in good agreement with observations. It is also confirmed that conditional symmetric instability (CSI) exists and is associated with the strengthening of the SJs at and after the mature stage of the simulated extratropical cyclone.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124142511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatial Complex Model for Wind Farm Site Assessment","authors":"K. Rozsavolgyi","doi":"10.2174/1874282300903010204","DOIUrl":"https://doi.org/10.2174/1874282300903010204","url":null,"abstract":"Our research is on the spatial allocation of possible wind energy usage. We would like to carry this out with a newly developed model (CMPAM = Complex Multifactoral Polygenetic Adaptive Model), which basically is a climate- oriented system, but other kind of factors are also considered. With this model those areas and terrains can be located where construction of wind farms would be reasonable. The wind field modeling core of CMPAM is mainly based on sequential Gaussian simulation (sGs) otherwise known as geostatistics. But concepts from atmospheric physics and Geographical Information Systems (GIS) are used as well. For application for Hungary WAsP generated 10 m wind speed data was used as input data. The geocorrection (geometric correction) of this data was performed by us. Using optimized variography and sGs, our results were applied for Hungary in different heights. Simulation results for different heights are summarized furthermore, an exponential regressive function describing the vertical wind profile was also established. From the complex analyses of CMPAM, results derived to the 100 m height are also included and explained in a map in this paper. This produces a basis for certain several possible sites for the utilization of wind energy, under given conditions.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131668095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trends in daily rainfall intensity over Israel 1950/1-2003/4.","authors":"Yizhak Yosef, H. Saaroni, P. Alpert","doi":"10.2174/1874282300903010196","DOIUrl":"https://doi.org/10.2174/1874282300903010196","url":null,"abstract":"The study focuses on long-term trends of daily rainfall in Israel as a function of their intensity in order to identify potential trends in rainfall extremity. The study period is the rainy season, October-May between 1950/1 and 2003/4. For the total rainfall, an increased trend is shown across Israel, especially for the central and southern regions, though non-significant. Daily rainfall intensity showed non-significant trends of increase in the heavy rainfall at the center and south and decrease at the north. The light to moderate rainfall trends increased in the north while they decreased at the center and south. Trends are significantly correlated with known teleconnection patterns, especially the East Atlantic- Western Russia and the North Sea-Caspian Sea patterns. Positive trends toward heavier rainfall are noted in Israel, which are significant in several specific locations. This finding has to be carefully followed since the region is a climatic border subjected to severe water shortage and is predicted to dry-up in most global warming scenarios. During the last decades there is an increasing evidence for more extreme rainfall at different places around the globe. Global warming was suggested to be linked with an increase in heavy rainfall due to an increase in atmospheric vapor and the warmer air. This trend is shown in the 4 th Assessment Report of the IPCC (1). In general, the Mediterranean Basin shows decreasing trends in the precipitation amount (2-4). The EM shows mixed rainfall trends but almost all stations show a decreasing trend in the precipitation which is especially large and significant during winter in the Greek, Cypriot and Turkish stations (5). Precipitation reduction over most Greek stations, combined with enhanced anticyclonic activity over almost the whole Mediterranean was found during the late 1980s and the early 1990s, a period characterized by high North Atlantic oscillation index values (6). Time series of extreme precipitation cases in Greece for the period 1970-2002, did not reveal significant positive or negative trend (7). Alpert et al. (8) showed the paradoxical increase of Mediterranean extreme daily rainfall in spite of the decrease in the total rainfall. They showed an increase in the torrential rainfall in Italy and Spain, heavy rainfall in Israel and heavy- torrential rainfall over Cyprus for the period 1951-1995. These trends were significant only in Italy and Spain. Kostopoulou and Jones (5) analyzed seasonal and annual trends over the central and Eastern Mediterranean (EM, 1958-2000). They showed statistically significant positive trends toward intense rainfall events and greater amount of precipitation for stations around the Italian Peninsula. For the EM, i.e., the Balkan Peninsula, western Turkey and","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134268133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trends in Chemical Composition of Wet Precipitation in Mexico City, Mexico: 1992-2007","authors":"A. Báez, R. Belmont, R. García, H. Padilla, M. Torres","doi":"10.2174/1874282300903010187","DOIUrl":"https://doi.org/10.2174/1874282300903010187","url":null,"abstract":"This paper presents the results of a study of variation in the chemical composition of wet precipitation over a 16-year period. The ions SO4 2- , NO3 - , Cl - , Ca 2+ , Mg 2+ K + , Na + , NH4 + and H + were analyzed. The correlation analysis showed a high positive correlation among these ions, indicating that anthropogenic emissions were the most important source. Trends in annual concentrations of SO4 2- , NO3 - , Cl - , NH4 + , Mg 2+ , Ca 2+ , K + , H + and alkalinity as function of time were calculated using a linear least-square regression of the volume weighted mean concentrations of these ions in rainwater collected over a 16-year period. Sulfate (SO4 2- ) in wet precipitation showed a significant decreasing trend, corresponding to the reduction in SO2 emissions in the Mexico City valley due to the change from oil to gas fuel in thermoelectric power plants and heavy and medium sized industries. In spite of the fact that the number of motor vehicles has risen considerably in Mexico City, NO3 - did not show a significant increasing trend. The NH4 + /Ca 2+ ratio showed a nearly significant increasing trend, due mainly to the significant decrease in Ca 2+ concentration. This decreasing trend was not as marked as that of SO4 2- . The contribution of NH4 + to neutralization was relatively small, showing only a non significant increase in NH4 + over the study period, while a considerable decreasing SO4 2- trend occurred, which could mean that part of the NH4 + ions reacted with other ions, forming ammonium compounds.","PeriodicalId":122982,"journal":{"name":"The Open Atmospheric Science Journal","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132651759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}