Dynamics behind warming of the southeastern Arabian Sea and its interruption based on in situ measurements     

Simi Mathew  Usha Natesan  Ganesan Latha  Ramasamy Venkatesan 《Ocean Dynamics》2018,68(4-5):457-467

A study of the inter-annual variability of the warming of the southeastern Arabian Sea (SEAS) during the spring transition months was carried out from 2013 to 2015 based on in situ data from moored buoys. An attempt was made to identify the roles of the different variables in the warming of the SEAS (e.g., net heat flux, advection, entrainment, and thickness of the barrier layer during the previous northeast monsoon season). The intense freshening of the SEAS (approximately 2 PSU) occurring in each December, together with the presence of a downwelling Rossby wave, supports the formation of a thick barrier layer during the northeast monsoon season. It is known that the barrier layer thickness, varying each year, plays a major role in the spring warming of the SEAS. Interestingly, an anomalously thick barrier layer occurred during the northeast monsoon season of 2012–2013. However, the highest sea surface temperature (31 °C) was recorded during the last week of April 2015, while the lowest sea surface temperature (29.7 °C) was recorded during the last week of May 2013. The mixed layer heat budget analysis during the spring transition months proved that the intense warming has been mainly supported by the net heat flux, not by other factors like advection and entrainment. The inter-annual variability analysis of the net heat flux and its components, averaged over a box region of the SEAS, showed a substantial latent heat flux release and a reduction in net shortwave radiation in 2013. Both factors contributed to the negative net heat flux. Strong breaks in the warming were also observed in May due to the entrainment of cold sub-surface waters. These events are associated with the cyclonic eddy persisting over the SEAS during the same time. The entrainment term, favoring the cooling, was stronger in 2015 than that in 2013 and 2014. The surface temperatures measured in 2013 were lower than those in 2014 and 2015 despite the presence of a thick barrier layer. The substantial decrease in net heat flux along with entrainment cooling has been identified as causes for this behavior.  相似文献   

Interferometric SAR for characterization of ravines as a function of their density, depth, and surface cover     

R.S. Chatterjee  S.K. Saha  Suresh Kumar  Sharika Mathew  R.C. Lakhera  V.K. Dadhwal 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(5):472-481

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Use of acoustic emissions to investigate localization in high-porosity sandstone subjected to true triaxial stresses   总被引：4，自引：3，他引：1  

Mathew D. Ingraham  Kathleen A. Issen  David J. Holcomb 《Acta Geotechnica》2013,8(6):645-663

Acoustic emissions were used to investigate the evolution of damage and strain localization in Castlegate sandstone specimens subjected to true triaxial states of stress, where the intermediate principal stress ranged from equal to minimum compression to equal to maximum compression. Three failure modes were observed: shear band formation at low mean stresses, compaction localization at intermediate stresses, and no localization at high mean stresses. For shear bands, the onset of localization consistently occurred prior to peak stress, while compaction localization initiated at the beginning of a stress plateau. The band angle (defined as the angle between the band normal and the maximum compression direction) determined by fitting a plane through the localized acoustic emission events corresponded well with the shear band angle expressed on the specimen jacket. As expected, the band angle decreased with increasing mean stress. The theoretically predicted dependence of band angle on deviatoric stress state was not confirmed; however, data scatter due to natural variations in material could obscure such a trend. Each failure mode displayed a unique acoustic emission rate response; therefore, this rate response alone can be used to determine the failure mode and the onset of localization in Castlegate sandstone.  相似文献   

The influence of the South-west Indian monsoon on continental deposition over the past 130 kyr, Gujarat, western India     

A.S. Khadkikar  G. Mathew  J.N. Malik  T.K. Gundu Rao  M.P. Chowgaonkar  S.S. Merh 《地学学报》1999,11(6):273-277

Ocean and ice core records of the intensity of the South-west Indian Monsoon (SwIM) show rapid shifts in most proxy indicators of climate over the past 125 kyr on decadal to millenial scales. However, the responses of continental environments to such perturbations remain unknown due to the absence of a suitable long-term continental record. The stratigraphic record from Gujarat, western India, an area where all sedimentological processes are governed by the vagaries of the SwIM, reveals three aggradation phases that represent deposits of seasonal rivers (AP1), ephemeral rivers (AP2) and dust storms (AP3). Based on a review of available dates and new ESR dates on the oldest exposed calcretes from palaeovertisols these phases are assigned the time brackets 135–100 kyr bp (AP1), 100–20 kyr bp (AP2) and 20–6 kyr bp (AP3). These results suggest that continental depositional environments respond in a subdued manner and are separated by thresholds. For climate shifts to effect durable changes in the continental depositional environment, a period between > 5 kyr and 16 kyr is the minimum time required to permanently change the landscape of an area. Alternatively, catastrophic changes in terrestrial depositional environments may also be effected by abrupt climatic shifts that are beyond the tolerance limits of the depositional systems.  相似文献   

Local-scale spatial modelling for interpolating climatic temperature variables to predict agricultural plant suitability     

Mathew A. Webb  Andrew Hall  Darren Kidd  Budiman Minansy 《Theoretical and Applied Climatology》2016,124(3-4):1145-1165

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North American extreme temperature events and related large scale meteorological patterns: a review of statistical methods,dynamics, modeling,and trends     

Richard Grotjahn  Robert Black  Ruby Leung  Michael F. Wehner  Mathew Barlow  Mike Bosilovich  Alexander Gershunov  William J. Gutowski  John R. Gyakum  Richard W. Katz  Yun-Young Lee  Young-Kwon Lim  Prabhat 《Climate Dynamics》2016,46(3-4):1151-1184

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Probabilistic seismic hazard map of Papua New Guinea     

Hadi Ghasemi  Chris McKee  Mark Leonard  Phil Cummins  Mathew Moihoi  Spiliopoulos Spiro  Felix Taranu  Eric Buri 《Natural Hazards》2016,81(2):1003-1025

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Kochi,India case study of climate adaptation to floods: Ranking local government investment options     

Supriya Mathew  Stefan Trück  Ann Henderson-Sellers 《Global Environmental Change》2012,22(1):308-319

Climate adaptation is uniquely linked to location, making it predominantly a local government and community responsibility. Despite the obligation to act, local governments are hindered by the absence of applicable guides to adaptation decision-making, especially adaptation to extreme events. In this paper, we describe a framework for prioritising adaptation options that could be locally implemented and illustrate it with a study of flooding in Kochi: a city in southern India. Unlike many demand driven, economics based studies, our new framework also incorporates non-economic dimensions of the extremes and potential adaptation options. Local knowledge is used to tackle data gaps and uncertainty related to extreme events: local experts select adaptation options that offer additional benefits besides those related to climate change. These co-benefits aid decision making under uncertainty by giving weight to community priorities. The Indian case study reveals that, risk evaluation and reduction need to be locally contextualised based on resources available, immediate community requirements, planning periods and local expert knowledge. Although there will be residual damage even after implementing selected options, we argue that, climate response will be most likely to be accepted when it also supports pressing needs.  相似文献   

Variability of soil moisture and its relationship with surface albedo and soil thermal diffusivity at Astronomical Observatory,Thiruvananthapuram, south Kerala   总被引：2，自引：0，他引：2  

M. S. Roxy  V. B. Sumithranand  G. Renuka 《Journal of Earth System Science》2010,119(4):507-517

Continuous observation data collected over the year 2008 at Astronomical Observatory, Thiruvananthapuram in south Kerala (76°59′E longitude and 8°30′N latitude) are used to study the diurnal, monthly and seasonal soil moisture variations. The effect of rainfall on diurnal and seasonal soil moisture is discussed. We have investigated relationships of soil moisture with surface albedo and soil thermal diffusivity. The diurnal variation of surface albedo appears as a U-shaped curve on sunny days. Surface albedo decreases with the increase of solar elevation angle, and it tends to be a constant when solar elevation angle is greater than 40°. So the daily average surface albedo was calculated using the data when solar elevation angle is greater than 40°. The results indicate that the mean daily surface albedo decreases with increases in soil moisture content, showing a typical exponential relation between the surface albedo and the soil moisture. Soil thermal diffusivity increases firstly and then decreases with the increase of soil moisture.  相似文献   

Acoustic Power Absorption and its Relation to Vector Magnetic Field of a Sunspot     

S. Gosain  S. K. Mathew  P. Venkatakrishnan 《Solar physics》2011,268(2):335-348

The distribution of acoustic power over sunspots shows an enhanced absorption near the umbra – penumbra boundary. Previous studies revealed that the region of enhanced absorption coincides with the region of strongest transverse potential field. The aim of this paper is to i) utilize the high-resolution vector magnetograms derived using Hinode SOT/SP observations and study the relationship between the vector magnetic field and power absorption and ii) study the variation of power absorption in sunspot penumbrae due to the presence of spine-like radial structures.  相似文献