Dhananjay A. Sant

Fractal dimensional analysis of Indian climatic dynamics

In this paper, we use fractal dimensional analysis to investigate the Indian climatic dynamics. We analyze time series data of three major dynamic components of the climate––temperature, pressure and precipitation. We study how climate variability changes from month to month and from one season to the other. We also investigate variability both at a local level (for individual stations) and at a regional level (for groups of stations). Our studies suggest that regional climatic models typically would not be able to predict local climate since they deal with averaged quantities. We find an interesting effect that precipitation during the south-west monsoon is affected by temperature and pressure variability during the preceding winter.

A climate predictability index and its applications

In this letter, a climate predictability index is proposed. It quantifies the predictability of three major components comprising the climate-temperature, pressure and precipitation. The quantification is done using a fractal dimensional analysis of the corresponding time series. The climate predictability index is calculated for 25 stations spread throughout India using the Global Historical Climatology Network dataset. Change in the index with the seasons suggests a strong influence of more than one climatic dynamics. In such cases, calculations done using mean yearly data are suspect. The index is shown to be useful in studying the interplay between various climatic components (viz. temperature, pressure and precipitation). Changes in predictability indices for temperature and pressure are seen to affect the index for precipitation. The index can be used as a discriminant for determining which stations are selected for use in developing regional climatic models.

Paleoclimatic data from 74KL and Guliya Cores: New insights

We analyze multi-proxy climatic records from the 74KL marine core and compare it with the delta(18)O record from: the Guliya ice core. These records have important implications for the evolution of the Southwest Monsoon System. We observe three distinct climatic events (viz. 19 ka to 13.5 ka, 13.5 ka to 10 ka and 3.4 ka to present) from the last glacial:phase to the present. Even though the first two events:are well documented in the literature, our combined analysis of data from both the cores suggests alternative mechanisms which could have complemented and strengthened these-events. The third, most recent event (occurring between 3.4 ka to present) does not seem to have been well documented earlier. We propose a possible mechanism to explain this event. We identify representative elements which better capture the above events as compared to more commonly used elements.

High resolution facies record on late Holocene flood plain sediments from lower reaches of Narmada Valley, Western India

A high resolution quantitative granulometric record for site Uchediya [21°43′2.22″ N, 73° 6′26.22″ E; 10 m a. s. l.] gives understanding towards accretion history of the late Holocene flood plain in the lower reaches of Narmada River. Two sediment facies (sandy and muddy) and seven subfacies (sandy subfacies: StMS+FS+CS, SmFS+MS, SlFS+VFS, and StMS + CS; muddy subfacies: FmSILT+VFS+FS, FmSILT+VFS (O) and FmSILT+VFS (T)) are identified based on cluster analysis supplemented with sedimentary structures observed in field and other laboratory data. Changes in hydrodynamics are further deduced based on various sedimentological parameters and their ratios leading to arrive at a depositional model.

Late holocene storm records from lower reaches of Narmada valley, Western India

Storms from the Arabian Sea are the most significant meteorological feature in western India that brings extreme rainy days together with catastrophic flooding. The present study reports two such palaeo-storm horizons at 1.16 m and 3.2 m above the present day water level in the Narmada channel, 56 km inland based on sedimentology and foraminiferal records. Both the horizons show similar sediment facies and foraminiferal assemblage. The present findings instigate to look for such new sites and build palaeo-storm records for western India.