scholarly journals Mapping the Coastal Upwelling East of Taiwan Using Geostationary Satellite Data

2021 ◽  
Vol 13 (2) ◽  
pp. 170
Author(s):  
Zhi Huang ◽  
Jianyu Hu ◽  
Weian Shi
Keyword(s):  
Summer Monsoon ◽  
East Coast ◽  
Coastal Upwelling ◽  
Monsoon Season ◽  
Geostationary Satellite ◽  
Sea Surface ◽  
Image Process ◽  
North Central ◽  
Topographic Position Index ◽  
Position Index

Coastal upwelling is important for coastal ecosystems and the blue economy because of its large productivity and large potential for catching fish. However, coastal upwelling along the Taiwan east coast has received little attention from the research community. This study used five-year daily Himawari-8 geostationary satellite sea surface temperature data to map the coastal upwelling east of Taiwan during the summer monsoon season. We applied a semi-automatic image process technique based on the topographic position index for the quantitative upwelling mapping. The results show clear evidence of seasonal coastal upwelling along the entire Taiwan east coast, mainly under the influence of upwelling-favorable southwesterly/southerly winds. There are three broad upwelling centers along the Taiwan east coast: north, central, and south. The upwelling around the northern center has the longest upwelling season, lasting from May to September. The upwelling extents are larger between June and August during the height of the summer monsoon.

Increasing aridity over the past 223 years in the Nepal Himalaya inferred from a tree-ring δ18O chronology

The Holocene ◽  
2011 ◽  
Vol 22 (7) ◽  
pp. 809-817 ◽  
Author(s):  
Masaki Sano ◽  
R Ramesh ◽  
MS Sheshshayee ◽  
R Sukumar
Keyword(s):  
Tree Ring ◽  
Summer Monsoon ◽  
Function Analysis ◽  
Monsoon Season ◽  
Sea Surface ◽  
Drought Severity ◽  
Sea Surface Temperatures ◽  
Nepal Himalaya ◽  
The Past ◽  
Surface Temperatures

A tree-ring δ18O chronology of Abies spectabilis from the Nepal Himalaya was established to study hydroclimate in the summer monsoon season over the past 223 years (ad 1778–2000). Response function analysis with ambient climatic records revealed that tree-ring δ18O was primarily controlled by the amount of precipitation and relative humidity during the monsoon season (June–September). Since tree-ring δ18O was simultaneously correlated with temperature, drought history in the monsoon season was reconstructed by calibrating against the Palmer Drought Severity Index (PDSI). Our reconstruction that accounts for 33.7% of the PDSI variance shows a decreasing trend of precipitation/moisture over the past two centuries, and reduction of monsoon activity can be found across different proxy records from the Himalaya and Tibet. Spatial correlation analysis with global sea surface temperatures suggests that the tropical oceans play a role in modulating hydroclimate in the Nepal Himalaya. Although the dynamic mechanisms of the weakening trend of monsoon intensity still remain to be analyzed, rising sea surface temperatures over the tropical Pacific and Indian Ocean could be responsible for the reduction of summer monsoon.

scholarly journals Relationship between Indian summer monsoon rainfall and sea surface temperature anomalies over equatorial central and eastern Pacific

MAUSAM ◽  
2021 ◽  
Vol 49 (2) ◽  
pp. 229-234
Author(s):  
V. THAPLIYAL ◽  
M. RAJEEVAN ◽  
S. R. PATIL
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Monsoon Rainfall ◽  
Indian Summer Monsoon Rainfall ◽  
Monsoon Season ◽  
Summer Monsoon Rainfall ◽  
Sea Surface ◽  
Sst Anomalies

Sea surface temperature (SST) variations over the three key regions over equatorial Pacific, viz., Nino (1+2), Nino 3 and Nino 4 and their relationships with Indian summer monsoon rainfall have been examined in this study. On monthly scale, SST anomalies over the three key regions show an oscillatory type of lagged correlations with Indian monsoon rainfall, positive correlations almost one year before the monsoon season (CC's are of the order of 0.3) which gradually change to significant negative correlation peaking in September/October during/after the monsoon season. The variations on seasonal scale also exhibit the same pattern of monthly variations but more smooth in nature. Composites of similar monsoon years show that during deficient (excess) monsoon years SST anomalies over all the three regions have warmer (cooler) trend which starts about 6 months prior to monsoon season. Tendencies of SST anomalies from previous winter (DJF) to summer (MAM) seasons over Nino 3 and Nino 4 regions are better predictors than EI-Nino categories currently being used in IMD's operational LRF model. By using tendency of SST over EI- Nino -4 region, in place of the category of EI-Nino, the 16 parameter operational Power Regression Model of IMD has been modified. The new forecast model shows better reduction in the forecast error.

scholarly journals Evolutions of sea level high and warm pool in the southeastern Arabian Sea and their association with Asian monsoons : A study on cause-and-effect relationships

MAUSAM ◽  
2021 ◽  
Vol 59 (1) ◽  
pp. 87-94
Author(s):  
O. P. SINGH
Keyword(s):  
Sea Level ◽  
Summer Monsoon ◽  
El Niño ◽  
Arabian Sea ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Warm Pool ◽  
Sea Surface ◽  
Southeastern Arabian Sea

The present study aims at gaining more insight into the evolution of warm pool and associated sea level dome in the southeastern Arabian Sea before the summer monsoon onset.  The results show that the Sea Surface Temperature (SST) maximum in the warm pool region is found during April close to the southwest coast of India.  The Sea Surface Height (SSH) maximum over the same region is observed during December. The collapse of sea level dome begins well in advance during the pre-monsoon whereas the warm pool collapses after the onset of summer monsoon during June.  Therefore, there is a lag of about three to four months between the collapses of the sea level high and the warm pool.  Most interesting aspect is the dramatic increase of SST from September and SSH from October which is continued throughout the post monsoon season (October - December). Therefore, both the collapse and evolution of warm pool are dramatic events before and after the summer monsoon.                    There are considerable variations in the intensity of warm pool and the height of sea level dome on interannual scale.  The variation during El-Nino Southern Oscillation (ENSO) epoch of 1987-88 has revealed many interesting features.  During El-Nino year 1987 the warm pool intensity reached its peak in June whereas during La Nina year 1988 the warm pool attained its maximum intensity much earlier, i.e., in April. 

scholarly journals Variation of summer monsoon rainfall over India in El-Ninos

MAUSAM ◽  
2021 ◽  
Vol 48 (3) ◽  
pp. 413-420
Author(s):  
D.A. MOOLEY
Keyword(s):  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Monsoon Season ◽  
Percent Level ◽  
Central India ◽  
Summer Monsoon Rainfall ◽  
Sea Surface ◽  
Pacific Region ◽  
The Pacific ◽  
Second Category

ABSTRACT. El Ninos which occurred during 1871-1990 are divided into two categories of events. The first category, EW, consists of the El Ninos in which the equatorial southeast (ESE) Pacific region (0-10° S; 80°W-180°W) experienced a Warn1ing phase as defined by suitable objective criteria, and the second category, E, consists of El Ninos in which the ESE Pacific region did not experience the warming phase. Sea surface temperature rise as well as anomaly over the Pacific region, summer monsoon rainfall over India and over its meteorological sub-divisions, in the categories EW and E are compared. Area-averaged rainfall of India for the summer monsoon season and for each of the months July and September are significantly (at 0.1 percent level) lower in EW events in comparison to those in E events. The summer monsoon rainfall of each of the 12 sub-divisions, from northwest and central India constituting about 50 per cent of the Indian plains, is significantly lower in EW events than that in E events, the highest rainfall deficiency in EW events being in the westernmost sub-divisions, i.e., West Rajasthan and Saurashtra-Kutch. Possible causes for the same have also been discussed.    

scholarly journals Environmental Effects on the Spatiotemporal Variability of Fish Larvae in the Western Guangdong Waters, China

2021 ◽  
Vol 9 (3) ◽  
pp. 316
Author(s):  
Yuting Feng ◽  
Lijun Yao ◽  
Hui Zhao ◽  
Jing Yu ◽  
Zhaojin Lin
Keyword(s):  
Environmental Effects ◽  
Coastal Upwelling ◽  
Fish Larvae ◽  
Additive Models ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Spatiotemporal Variability ◽  
Aquatic Life ◽  
Positive Effects ◽  
Fishery Resources

Spawning grounds occupy an important position in the survival and reproduction of aquatic life, which plays an important role in the replenishment of fishery resources, especially in the China coasts where fishery resources are depleting. This study investigated environmental effects on the spatiotemporal variability of fish larvae in the western Guangdong waters (WGWs), on the basis of generalized additive models (GAMs) and center of gravity (CoG). Satellite data including sea surface salinity (SSS), sea surface temperature (SST), and in situ observations for fish larvae from April to June in 2014–2015 were used. Results showed that 40.3% of the total variation in fish larvae density was explained. SST, SSS, and depth showed positive effects in 23–24 °C and 27–30 °C, 24–32 PSU, and 0–60 m, and showed negative effects in 24–27 °C, 32–34.2 PSU, 60–80 m. Based on the stepwise GAMs, the most important factor was month, with a contribution of 10.6%, followed by longitude, offshore distance, depth, and latitude, with contributions of 7.0%, 7.0%, 6.3%, 4.2%, 3.9%, and 1.3%, respectively. Fish larvae CoG shifted northward by 0.6° N and eastwards by 0.13° E from April to June. The distribution of fish larvae in the WGWs was affected by complex submarine topography in the Qiongzhou Strait, coastal upwelling in the WGWs, and runoff from the Pearl River.

scholarly journals Anthropogenic warming and intraseasonal summer monsoon variability amplify the risk of future flash droughts in India

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Vimal Mishra ◽  
Saran Aadhar ◽  
Shanti Shwarup Mahto
Keyword(s):  
Soil Moisture ◽  
Summer Monsoon ◽  
Crop Production ◽  
Monsoon Rainfall ◽  
Root Zone ◽  
Monsoon Season ◽  
Intraseasonal Variability ◽  
Positive Temperature ◽  
Groundwater Abstraction ◽  
Increased Risk

AbstractFlash droughts cause rapid depletion in root-zone soil moisture and severely affect crop health and irrigation water demands. However, their occurrence and impacts in the current and future climate in India remain unknown. Here we use observations and model simulations from the large ensemble of Community Earth System Model to quantify the risk of flash droughts in India. Root-zone soil moisture simulations conducted using Variable Infiltration Capacity model show that flash droughts predominantly occur during the summer monsoon season (June–September) and driven by the intraseasonal variability of monsoon rainfall. Positive temperature anomalies during the monsoon break rapidly deplete soil moisture, which is further exacerbated by the land-atmospheric feedback. The worst flash drought in the observed (1951–2016) climate occurred in 1979, affecting more than 40% of the country. The frequency of concurrent hot and dry extremes is projected to rise by about five-fold, causing approximately seven-fold increase in flash droughts like 1979 by the end of the 21st century. The increased risk of flash droughts in the future is attributed to intraseasonal variability of the summer monsoon rainfall and anthropogenic warming, which can have deleterious implications for crop production, irrigation demands, and groundwater abstraction in India.

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