M. Orlić, T. Leder, V. Vujnović, D. Herak, Vesna Denić-Jukić, K. Horvath, B. Grbec, G. B. Paklar, M. Herak
{"title":"Report of the Croatian Committee of Geodesy and Geophysics on activities carried out between 2011 and 2014","authors":"M. Orlić, T. Leder, V. Vujnović, D. Herak, Vesna Denić-Jukić, K. Horvath, B. Grbec, G. B. Paklar, M. Herak","doi":"10.15233/GFZ.2015.32.7","DOIUrl":"https://doi.org/10.15233/GFZ.2015.32.7","url":null,"abstract":"","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"32 1","pages":"133-174"},"PeriodicalIF":1.0,"publicationDate":"2015-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67352387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents the effects of geometry of sediment bedrock interface (GSBI) of 3D basins with a circular outcropping free surface on the characteristics and the focusing of the basin-generated surface (BGS) waves and associated spatial variations of the average spectral amplification (ASA) and average aggravation factor (AAF). An increase of ASA towards the centre of the semispherical (SS-) basin as compared to the 2D basin revealed the focusing of the BGS-waves in the SS-basin. The obtained 2.8 times larger ASA at the centre of the SS-basin to that of 2D basin calls for a special attention in predicting the seismic hazard in such basins for earthquake engineering purposes. The analysis of the simulated results revealed that the amplitude amplification due to the focusing of the BGS-waves was highly affected by the GSBI. For example, the ASA at the centre of a trapezoidal basin with edge slope 20° was 50% larger than that at the centre of a trapezoidal basin with edge slope 45°. It is recommended to compute the AAF using the same components of ground motion as that of the incident wave to conservatively aggravate the ground motion to incorporate the 3D basin-effects in the seismic microzonation where it is over based on the 1D response of sediment column.
{"title":"Quantification of effects of geometry of sediment bedrock interface on ground motion in 3D basin with circular free surface","authors":"J. Narayan, Battan Kamal","doi":"10.15233/GFZ.2015.32.3","DOIUrl":"https://doi.org/10.15233/GFZ.2015.32.3","url":null,"abstract":"This paper presents the effects of geometry of sediment bedrock interface (GSBI) of 3D basins with a circular outcropping free surface on the characteristics and the focusing of the basin-generated surface (BGS) waves and associated spatial variations of the average spectral amplification (ASA) and average aggravation factor (AAF). An increase of ASA towards the centre of the semispherical (SS-) basin as compared to the 2D basin revealed the focusing of the BGS-waves in the SS-basin. The obtained 2.8 times larger ASA at the centre of the SS-basin to that of 2D basin calls for a special attention in predicting the seismic hazard in such basins for earthquake engineering purposes. The analysis of the simulated results revealed that the amplitude amplification due to the focusing of the BGS-waves was highly affected by the GSBI. For example, the ASA at the centre of a trapezoidal basin with edge slope 20° was 50% larger than that at the centre of a trapezoidal basin with edge slope 45°. It is recommended to compute the AAF using the same components of ground motion as that of the incident wave to conservatively aggravate the ground motion to incorporate the 3D basin-effects in the seismic microzonation where it is over based on the 1D response of sediment column.","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"32 1","pages":"1-25"},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67351838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Appropriate and acceptable prediction of bed load being carried by streams is vitally important for water resources quantity and quality studies. Although measuring the rate of bed load in situ is the most consistent method, it is very expensive and cannot be conducted for as many streams as the measurement of suspended sediment load. Therefore, in this study the role of suspended load on bedload prediction was examined by using sensitivity analysis. On the other hand, conventional sediment rating curves and equations can not predict sediment load accurately so recently the usage of machine learning algorithms increase rapidly. Accordingly, soft computational methods are used in the study. These are; artificial neural network (ANN), support vector machine (SVM) models and a decision tree (CHAID) model that is not used before in sediment studies. Some particular parameters are frequently used in these soft computational methods to form input sets. Hence, well known and commonly used three input sets and a new generated set are used as inputs to predict bedload and then the suspended load variable is added in these input sets. The performances of models with respect to input sets are compared to each other. To generate the results and to push the limits of models a very skewed and heterogeneous data is collected from distributed locations. The results indicate that the performance of ANN and CHAID tree models are good when compared to SVM models. The usage of a suspended load as an additional input for the models boosts the model performances and the suspended load has significant contributions to all models.
{"title":"Prediction of bed load via suspended sedimentload using soft computing methods","authors":"A. Pektas, E. Doğan","doi":"10.15233/GFZ.2015.32.2","DOIUrl":"https://doi.org/10.15233/GFZ.2015.32.2","url":null,"abstract":"Appropriate and acceptable prediction of bed load being carried by streams is vitally important for water resources quantity and quality studies. Although measuring the rate of bed load in situ is the most consistent method, it is very expensive and cannot be conducted for as many streams as the measurement of suspended sediment load. Therefore, in this study the role of suspended load on bedload prediction was examined by using sensitivity analysis. On the other hand, conventional sediment rating curves and equations can not predict sediment load accurately so recently the usage of machine learning algorithms increase rapidly. Accordingly, soft computational methods are used in the study. These are; artificial neural network (ANN), support vector machine (SVM) models and a decision tree (CHAID) model that is not used before in sediment studies. Some particular parameters are frequently used in these soft computational methods to form input sets. Hence, well known and commonly used three input sets and a new generated set are used as inputs to predict bedload and then the suspended load variable is added in these input sets. The performances of models with respect to input sets are compared to each other. To generate the results and to push the limits of models a very skewed and heterogeneous data is collected from distributed locations. The results indicate that the performance of ANN and CHAID tree models are good when compared to SVM models. The usage of a suspended load as an additional input for the models boosts the model performances and the suspended load has significant contributions to all models.","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"32 1","pages":"27-46"},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67352099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Jean-Francois Geleyn (1950-2015)","authors":"A. Marki, M. T. Prtenjak, B. Grisogono","doi":"10.15233/GFZ.2015.32.6","DOIUrl":"https://doi.org/10.15233/GFZ.2015.32.6","url":null,"abstract":"","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"32 1","pages":"129-131"},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67352787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Bibliografija članaka, izvješća i knjiga koje je objavio Stjepan Mohorovičić","authors":"M. Orlić, Ivana Vrkić","doi":"10.15233/GFZ.2015.32.4","DOIUrl":"https://doi.org/10.15233/GFZ.2015.32.4","url":null,"abstract":"","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"32 1","pages":"93-127"},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67351957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper reports the estimated response of hourly mean concentrations of selected air pollutants, namely carbon monoxide (CO), sulphur dioxide (SO2), nitrogen dioxide (NO2) and particulate matter with an aerodynamic diameter of up to 10 μm (PM10), to local scale meteorology in Zagreb, Croatia for the period 2006–2012. A new method is applied here for the urban area of Zagreb. In a general model, a logarithm of hourly mean air pollutant concentrations is expressed as the sum of the nonlinear functions of meteorological and several time variables, with the latter included accounting for temporal variation in emissions. The model can be formulated within the framework of generalized additive models (GAMs) and is additive on the logarithmic scale, which results in multiplicative effects on the original scale. Although the model is nonlinear, it is simple and easy to interpret. It quantifies the impact of meteorological conditions and emissions on air pollution. A measure of the relative importance of each predictor, partial effects and statistical evaluation of the model are also presented. Overall, the results show that the most important predictors are those related to emissions. The aggregate impact of meteorological variables in the model explained 45% of variance in CO, 14% in SO2, 25% in NO2 and 24% in PM10. This indicates that meteorology, at least on a local scale, is a noticeable driver of air quality in Zagreb. Stable atmospheric conditions in the urban area favour the occurrence of higher concentrations of air pollutants. Convection processes dominate under unstable conditions, resulting in the dilution of pollutant concentrations within the boundary layer.
{"title":"Using a generalized additive model to quantify the influence of local meteorology on air quality in Zagreb","authors":"Andreina Belušić, Ivana Herceg-Bulić, Z. Klaic","doi":"10.15233/GFZ.2015.32.5","DOIUrl":"https://doi.org/10.15233/GFZ.2015.32.5","url":null,"abstract":"This paper reports the estimated response of hourly mean concentrations of selected air pollutants, namely carbon monoxide (CO), sulphur dioxide (SO2), nitrogen dioxide (NO2) and particulate matter with an aerodynamic diameter of up to 10 μm (PM10), to local scale meteorology in Zagreb, Croatia for the period 2006–2012. A new method is applied here for the urban area of Zagreb. In a general model, a logarithm of hourly mean air pollutant concentrations is expressed as the sum of the nonlinear functions of meteorological and several time variables, with the latter included accounting for temporal variation in emissions. The model can be formulated within the framework of generalized additive models (GAMs) and is additive on the logarithmic scale, which results in multiplicative effects on the original scale. Although the model is nonlinear, it is simple and easy to interpret. It quantifies the impact of meteorological conditions and emissions on air pollution. A measure of the relative importance of each predictor, partial effects and statistical evaluation of the model are also presented. Overall, the results show that the most important predictors are those related to emissions. The aggregate impact of meteorological variables in the model explained 45% of variance in CO, 14% in SO2, 25% in NO2 and 24% in PM10. This indicates that meteorology, at least on a local scale, is a noticeable driver of air quality in Zagreb. Stable atmospheric conditions in the urban area favour the occurrence of higher concentrations of air pollutants. Convection processes dominate under unstable conditions, resulting in the dilution of pollutant concentrations within the boundary layer.","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"32 1","pages":"47-77"},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15233/GFZ.2015.32.5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67352041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Subjective thermal sensation of late teenagers was examined aiming to reveal potential discrepancies in its estimation compared to adults. Since teenagers have different clothing habits and preferences from adults, it is important to know whether the conclusions reached by studies on thermal sensation, usually involving adults, can be also applied to teenagers. A group of late teenagers was interviewed, based on a structured questionnaire, in an outdoor environment during two winter days and under an unexpected Saharan dust transport event during the second day, while meteorological measurements were obtained by the closest to the interview site weather station. Moreover, the performance of the bioclimatic index Cooling Power in simulating subjects’ thermal sensation was evaluated. Although differences in clothing thermal insulation of late teenagers compared to that suggested by similar studies were recognized, generally the results of this study were in agreement with the findings of similar field surveys focusing on individual thermal sensation and with no evidence of effects of the dust transport event on thermal sensation. Cooling Power based on the Mediterranean thermal sensation scale predicted thermal sensation vote fairly well.
{"title":"Thermal perception of teenagers in a cool outdoor environment: A case study","authors":"K. Pantavou, A. Mavrakis","doi":"10.15233/GFZ.2015.32.1","DOIUrl":"https://doi.org/10.15233/GFZ.2015.32.1","url":null,"abstract":"Subjective thermal sensation of late teenagers was examined aiming to reveal potential discrepancies in its estimation compared to adults. Since teenagers have different clothing habits and preferences from adults, it is important to know whether the conclusions reached by studies on thermal sensation, usually involving adults, can be also applied to teenagers. A group of late teenagers was interviewed, based on a structured questionnaire, in an outdoor environment during two winter days and under an unexpected Saharan dust transport event during the second day, while meteorological measurements were obtained by the closest to the interview site weather station. Moreover, the performance of the bioclimatic index Cooling Power in simulating subjects’ thermal sensation was evaluated. Although differences in clothing thermal insulation of late teenagers compared to that suggested by similar studies were recognized, generally the results of this study were in agreement with the findings of similar field surveys focusing on individual thermal sensation and with no evidence of effects of the dust transport event on thermal sensation. Cooling Power based on the Mediterranean thermal sensation scale predicted thermal sensation vote fairly well.","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"32 1","pages":"79-92"},"PeriodicalIF":1.0,"publicationDate":"2015-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67351539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Local wind changes within the flow of the Adriatic Bora are investigated in the case of 8 December 2001 that was simulated with the WRF/ARW model in a 333 m horizontal resolution and with all relevant model variables archived during a 3 h time interval with 1 s temporal resolution. Along a selected cross section, two locations of strong gusts in the lee of a Dinaric mountain ridge are found – the upper one on the slope and the other over the sea close to the coastline; in between the wind is considerably weaker. About 16 to 18 gusts developed in the 3 h interval at both locations with an average period of approximately 8.5 min. The advective transport of kinetic energy (KE), the work of the unbalanced part of the pressure gradient force and the diffusion and dissipation of KE cause the local change D KE, and their quasi-periodic fluctuations lead to gusts and lulls. The results of the numerical simulation enable an estimation of the contributions of advection, the work of forces and of turbulence and dissipation effects. Advective contributions to local changes are more or less in the phase with DKE and ahead of the phase of KE, while the contributions of work are generally smaller and in the opposite phase: so in general the advection and the work effects oppose each other. The advection and the work effects are not spatially homogeneous, i.e. they cease and even change their sign between the two locations of the strongest gusts and so there is no continuous displacement of KE from the upper to the lower location by either of the two effects: their contributions interchange with each other down the slope.
{"title":"The role of advection and of work done by forces in the gustiness of the Bora flow","authors":"J. Rakovec, R. Žabkar, M. Žagar","doi":"10.15233/GFZ.2014.31.5","DOIUrl":"https://doi.org/10.15233/GFZ.2014.31.5","url":null,"abstract":"Local wind changes within the flow of the Adriatic Bora are investigated in the case of 8 December 2001 that was simulated with the WRF/ARW model in a 333 m horizontal resolution and with all relevant model variables archived during a 3 h time interval with 1 s temporal resolution. Along a selected cross section, two locations of strong gusts in the lee of a Dinaric mountain ridge are found – the upper one on the slope and the other over the sea close to the coastline; in between the wind is considerably weaker. About 16 to 18 gusts developed in the 3 h interval at both locations with an average period of approximately 8.5 min. The advective transport of kinetic energy (KE), the work of the unbalanced part of the pressure gradient force and the diffusion and dissipation of KE cause the local change D KE, and their quasi-periodic fluctuations lead to gusts and lulls. The results of the numerical simulation enable an estimation of the contributions of advection, the work of forces and of turbulence and dissipation effects. Advective contributions to local changes are more or less in the phase with DKE and ahead of the phase of KE, while the contributions of work are generally smaller and in the opposite phase: so in general the advection and the work effects oppose each other. The advection and the work effects are not spatially homogeneous, i.e. they cease and even change their sign between the two locations of the strongest gusts and so there is no continuous displacement of KE from the upper to the lower location by either of the two effects: their contributions interchange with each other down the slope.","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"109 1","pages":"81-103"},"PeriodicalIF":1.0,"publicationDate":"2014-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15233/GFZ.2014.31.5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67351787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chisomo Patrick Kumbuyo, H. Yasuda, Y. Kitamura, K. Shimizu
Inter annual fluctuation of rainfall in Malawi was studied using a 31 year time series from selected rain gauge stations with the aim of analyzing the spatial and temporal characteristics of rainfall in Malawi. The study found strong inter-annual fluctuation of rainfall, with topography and location playing major roles in the annual rainfall distribution. The seasonal index and precipitation concentration index showed that rainfall is highly seasonal and highly concentrated with most stations receiving rainfall in three months, except for Nkhatabay which has seasonal rainfall. The intra annual rainfall distribution was highly variable in time and space. Cross correlations among the stations suggested two distinct zones, zone 1 composed of Karonga and Nkhatabay and zone 2 composed of Bolero, Kasungu, Salima, Dedza, Mangochi, Makoka and Ngabu. Spectral analysis of the rainfall time series revealed cycles at five to eight years, suggesting links with the El Nino Southern Oscillation and double the period of the Quasi Biennial Oscillation. Apart from the common cycles, the rainfall time series of the two zones showed periods of 13.64 and 10.06 years, respectively, which suggests links with the solar cycle. These cycles are consistent with those found in other southern Africa countries.
{"title":"Fluctuation of rainfall time series in Malawi: An analysis of selected areas","authors":"Chisomo Patrick Kumbuyo, H. Yasuda, Y. Kitamura, K. Shimizu","doi":"10.15233/GFZ.2014.31.1","DOIUrl":"https://doi.org/10.15233/GFZ.2014.31.1","url":null,"abstract":"Inter annual fluctuation of rainfall in Malawi was studied using a 31 year time series from selected rain gauge stations with the aim of analyzing the spatial and temporal characteristics of rainfall in Malawi. The study found strong inter-annual fluctuation of rainfall, with topography and location playing major roles in the annual rainfall distribution. The seasonal index and precipitation concentration index showed that rainfall is highly seasonal and highly concentrated with most stations receiving rainfall in three months, except for Nkhatabay which has seasonal rainfall. The intra annual rainfall distribution was highly variable in time and space. Cross correlations among the stations suggested two distinct zones, zone 1 composed of Karonga and Nkhatabay and zone 2 composed of Bolero, Kasungu, Salima, Dedza, Mangochi, Makoka and Ngabu. Spectral analysis of the rainfall time series revealed cycles at five to eight years, suggesting links with the El Nino Southern Oscillation and double the period of the Quasi Biennial Oscillation. Apart from the common cycles, the rainfall time series of the two zones showed periods of 13.64 and 10.06 years, respectively, which suggests links with the solar cycle. These cycles are consistent with those found in other southern Africa countries.","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"31 1","pages":"13-28"},"PeriodicalIF":1.0,"publicationDate":"2014-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15233/GFZ.2014.31.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67351521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Subhendu Brata Saha, S. Roy, S. Bhowmik, P. K. Kundu
The intra-seasonal variability of the Indian summer monsoon, which manifests in the form of “active” and “break” phases in rainfall, is investigated with respect to the variability of the convective and stratiform precipitating cloud pattern over the region. Long period data from TRMM PR satellite (2A23 and 3B42 datasets) for the monsoon season of 2002 to 2010 over the Indian subcontinent is used for this purpose. The study reveals that the most significant spatial variation in convective and stratiform cloud amount in relation to the active and break phase occurs over the monsoon trough region in central India. The active phase is characterized by positive convective (~5%) and stratiform (~20%) precipitating cloud anomalies over this region. However, the maximum of the former precedes the latter by 1–2 days leading up to the active phase, indicating that the stratiform build up, is due to the gradual organization of the convective cloud systems over the region. The days leading up to the break phase are marked by negative anomalies in the convective and stratiform fractions of cloudiness over this region, which are in phase with each other, unlike the lead-up to the active phase. Analysis of the pattern of atmospheric heat source and sinks over the region from the NCEP–NCAR re-analysis data indicates that the engine for the growth/decay of convection over the monsoon trough region lies primarily in the Bay of Bengal and adjacent east India. The active phase is preceded by a heating pattern that promotes large scale, organized convective cloud growth over the Bay of Bengal preceding the actual onset, while the heating pattern leading up to the break phase promotes the formation of isolated convective clouds and decay of cloud organization over the monsoon trough region.
{"title":"Intra-seasonal variability of cloud amount over the Indian subcontinent during the monsoon season as observed by TRMM precipitation radar","authors":"Subhendu Brata Saha, S. Roy, S. Bhowmik, P. K. Kundu","doi":"10.15233/GFZ.2014.31.2","DOIUrl":"https://doi.org/10.15233/GFZ.2014.31.2","url":null,"abstract":"The intra-seasonal variability of the Indian summer monsoon, which manifests in the form of “active” and “break” phases in rainfall, is investigated with respect to the variability of the convective and stratiform precipitating cloud pattern over the region. Long period data from TRMM PR satellite (2A23 and 3B42 datasets) for the monsoon season of 2002 to 2010 over the Indian subcontinent is used for this purpose. The study reveals that the most significant spatial variation in convective and stratiform cloud amount in relation to the active and break phase occurs over the monsoon trough region in central India. The active phase is characterized by positive convective (~5%) and stratiform (~20%) precipitating cloud anomalies over this region. However, the maximum of the former precedes the latter by 1–2 days leading up to the active phase, indicating that the stratiform build up, is due to the gradual organization of the convective cloud systems over the region. The days leading up to the break phase are marked by negative anomalies in the convective and stratiform fractions of cloudiness over this region, which are in phase with each other, unlike the lead-up to the active phase. Analysis of the pattern of atmospheric heat source and sinks over the region from the NCEP–NCAR re-analysis data indicates that the engine for the growth/decay of convection over the monsoon trough region lies primarily in the Bay of Bengal and adjacent east India. The active phase is preceded by a heating pattern that promotes large scale, organized convective cloud growth over the Bay of Bengal preceding the actual onset, while the heating pattern leading up to the break phase promotes the formation of isolated convective clouds and decay of cloud organization over the monsoon trough region.","PeriodicalId":50419,"journal":{"name":"Geofizika","volume":"31 1","pages":"29-53"},"PeriodicalIF":1.0,"publicationDate":"2014-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.15233/GFZ.2014.31.2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67351668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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