1. ªengörür, B., C. Dede and E. Doğan: The examination of the performances of methods used in separating the total stream flow in different rivers.
In this study, the performances of methods of flow separation into the surface flow and base flow of the total stream flow in rivers with different hydraulic features have been examined. For this purpose, daily mean stream flow data of Büyük Melen and Aksu Rivers which are in the same watershed but with different features (average flow value, catchment area, mean elevation) have been separated as surface flow and base flow with the use of Digital Filtering Method (DFM) and United Kingdom Institute of Hydrology Method (UKIH). The recession coefficient in DFM has been used as α = 0.830; and the number of elements for the groups formed to determine the turning points of flow data in UKIH has been used as N = 5. The study has revealed that the results of surface and base flows obtained by both flow separation methods show similarity in all rivers in an acceptable level; and the surface flow values agree better (R2 > 0,76) compared to base flow values (R2 > 0.63). However, it has been seen that as long as the total flow values decrease, the surface flow results for both methods come closer to each other; but the results of base flow get differentiated. This situation has been clearly seen in the results of surface (R2 > 0.89) and base (R2 > 0.63) flows belonging to Aksu River which has lower values of flow when compared to the ones of Büyük Melen River.
Keywords: separation of flow, surface flow, base flow, DFM, UKIH
2. Kumbuyo, C. P., H. Yasuda, Y. Kitamura and K. Shimizu: Fluctuation of rainfall time series in Malawi: An analysis of selected areas.
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.
Keywords: bimodal rainfall, inter annual fluctuation, seasonal index, precipitation concentration index, spectral analysis
3. Saha, S. B., S. Sen Roy, S. K. Roy Bhowmik and P. K. Kundu: Intra-seasonal variability of cloud amount over the Indian subcontinent during the monsoon season as observed by TRMM precipitation radar.
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.
Keywords: intra-seasonal variability, TRMM Precipitation Radar; Indian summer monsoon, active break phases, convective cloud, stratiform cloud, heatsource, heat sink
4. Ru¾iæ, I. and I. Herceg-Buliæ: Influence of soil moisture and dynamic vegetation coupling on numerical simulations of surface temperature, precipitation and evaporation over the Europe.
In this paper we explore the impact of vegetation cover and soil moisture coupling on climate simulations over the Europe. For this purpose, the International Centre for Theoretical Physics (ICTP) atmospheric general circulation model (AGCM) is used. The analysis is based on three targeted simulations for the period 1981-2010: a control experiment (with a simple land-surface model that mimics interaction of soil and atmosphere); an experiment with land-surface temperature and soil moisture coupling, and an experiment with both soil moisture and interactive vegetation coupling. The amplitude and interannual variability of surface air temperature, precipitation and evaporation for summer and winter seasons are examined. Compared to the control experiment, increasing of surface temperature over the continental Europe is found for the experiment with soil-moisture model for both, winter and summer seasons. However, when ICTP AGCM is coupled with the dynamic vegetation model, increasing of surface temperature is simulated only during the summer, while it is reduced during the winter. Generally, the dynamic vegetation model reduces total precipitation over the observed domain, and areas with the most pronounced decrease of the total precipitation coincide with areas of reduced evaporation. The results indicate substantial impact of soil moisture and vegetation coupling on amplitudes of simulated surface air temperature, precipitation and evaporation with predominant contribution of the soil moisture coupling. Contrary, the impact on the interannual variability of analyzed variables is rather weak.
Keywords: ICTP AGCM model, soil moisture model, dynamic vegetation model, surface air temperature, precipitation, evaporation, interannual variability