Spring Extreme Precipitation Days in North China and Their Reliance on Atmospheric Circulation Patterns During 1979–2019

The interannual variation of springtime extreme precipitation (SEP) days in North China (NC) and their reliance on atmospheric circulation patterns are studied by using the continuous daily record of 396 rain gauges and the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis during 1979–2019. The SEP days are defined as the days when at least 10% of rain gauges in NC record daily precipitation no less than 10.5 mm. Results show that the number of SEP days shows large interannual variability but no significant trend in the study period. Using the objective classification method of the obliquely rotated principal analysis in T-mode, we classify the atmospheric circulation into five different patterns based on the geopotential height at 700 hPa. Three circulation patterns all have fronts and are associated with strong southerly wind, leading to 88% of SEP days in NC. The strong southerly wind may provide moisture and dynamic forcing for the frontal precipitation. The interannual variation of SEP days is related with the number of the three above-mentioned dominant circulation patterns. Further analysis shows that the West Pacific pattern could be one of the possible climate variability modes related to SEP days. This study reveals that the daily circulation pattern may be the linkage between SEP days and climate variability modes in NC.

Factors Influencing the Interannual Variation in Biomass of Bottom-Cultured Yesso Scallop (Patinopecten yessoensis) in the Changhai Sea Area, China

Understanding how environmental factors impact the interannual variation in scallop growth and subsequently developing an easily obtained parameter to indicate this variation could provide a scientific basis for optimizing their aquaculture. In this study, we have set a growth scenario of uniformly sowed scallops of the same initial size in the Changhai sea area. The Yesso scallop culture ecosystem model was used to simulate the growth of bottom-cultured Yesso scallop each year from December 1, 2006 to November 30, 2017. The results show that the annual growth rate was higher in the northwest than in the southeast, and there were obvious high-value areas near the islands. The scallop biomass was significantly lower in 2009–2010 and reached its highest point in 2013–2014. Based on the match-mismatch conditions of bottom-water temperature, food availability, and the Yesso scallop growth process, three factors were determined: suitable growth days (SGD), restricted growth days (RGD), and food accumulation (FA). Subsequently, a multiple regression relationship was proposed with scallop biomass to explore the reasons affecting the interannual variations in scallop growth. We found that the anomaly of the contribution of SGD and FA for the scallop growth was small, and the interannual variation in scallop biomass was mainly regulated by RGD in winter. Our results indicated that the interannual variation in RGD in winter was closely related to the regional averaged air temperature in early winter. The air temperature in early winter is easily obtained in practice. Consequently, it could be used to predict the interannual growth of bottom-cultured scallops to improve aquaculture planning and management.

Quantitative Analysis of Vegetation Dynamics in Response to Climatic Factors and Human Activities in Southwest China

We determined the time scale of normalized difference vegetation index (NDVI) response to drought and used trend and correlation analyses to explore the spatial and temporal variability characteristics of the NDVI and SPEI and their sensitivity to climatic factors in southwest China from 2000 to 2020. We used a partial derivative approach to calculate the contributions of six climatic factors and human activities to the interannual variation in the NDVI. The results demonstrated that from 2000 to 2020, the annual mean NDVI in southwest China showed a slight decreasing trend at a rate of 0.0001 y−1. The NDVI had the highest sensitivity to the standardized precipitation and evapotranspiration index on a 12-month time scale. The NDVI exhibited a 1-year delayed response to drought. The SPEI has the highest sensitivity to precipitation. The percentage of pixels with a positive correlation between NDVI and precipitation, mean temperature, temperature difference, mean relative humidity, mean wind speed, and sunshine duration in the study area was 31.73%, 46.81%, 35.49%, 25.76%, 39.36%, and 39.89%, respectively. The average contributions of these six climatic factors to the interannual variation of NDVI were 0.00029, 0.00046, −0.00007, 0.00007, 0.0008, and 0.00001 y−1, respectively. The NDVI had the highest sensitivity to mean temperature and the lowest sensitivity to mean relative humidity. The average contributions of climatic factors and human activities to interannual variability in southwest China were 0.00156 and 0.00012 y−1, respectively. The positive influence of climatic factors on the NDVI was stronger than that of human activities. This study provides a theoretical basis for the sustainable management of the regional ecological environment.

Global distribution and interannual variation in the winter halocline

The distribution and interannual variation in the winter halocline in the upper layers of the world ocean were investigated via analyses of hydrographic data from the World Ocean Database 2013 using a simple definition of the halocline. A halocline was generally observed in the tropics, equatorward portions of subtropical regions, subarctic North Pacific and Southern Ocean. A strong halocline tended to occur in areas where the sea surface salinity (SSS) was low. The interannual variation in halocline strength was correlated with variation in SSS. The correlation coefficients were usually negative: the halocline was strong when the SSS was low. However, in the Gulf of Alaska in the northeastern North Pacific, the correlation coefficient was positive. There, halocline strength was influenced by interannual variation in Ekman pumping.

Floods in Karnataka during 2009 : A synoptic study

Karnataka a State in south peninsular India receives 73% of its annual rainfall during southwestmonsoon season. Because of the complex physiographical features, the rainfall pattern over the State shows large spatialvariation from 50 to 350 cms. The coefficient of interannual variation of the monsoon rainfall is about 15% over coastalKarnataka (CK) and between 20-30% over interior Karnataka. The precipitation over this State is mainly dominated bysemi permanent systems like off shore trough running along the west coast, low pressure systems forming over the Bay ofBengal during the monsoon season. A well marked low pressure area during 28 September - 3 October 2009 over the Bayof Bengal caused widespread damage to life and property in north Karnataka. In this study, an attempt has been made toexamine the synoptic features of this system that caused heavy rainfall over many districts of the State leading towidespread destruction.

Effects of Livestock Grazing on Interannual Variation of Soil Methane Uptake in an Inner Mongolian Meadow Steppe

Background and aims. This study aimed at identifying the effects of livestock grazing on interannual variation in soil CH4 uptake and underlying mechanisms in a meadow steppe ecosystem. Methods. A multi-year grazing experiment subject to six stocking rates was conducted to quantify CH4 fluxes as well as the changes in driving factors: vegetation traits, soil physicochemical properties and climatic parameters. The closed static chamber technique and a gas chromatograph were used to measure methane fluxes. Multivariate regression analysis was performed to explore empirical relationships. Results. With increasing stocking rate, the multi-year mean CH4 uptake rate decreased in a sigmoid curve-shaped manner, with the threshold point appearing in the light grazing treatment. The interannual changes in soil CH4 uptake were highly dependent on stocking rate, with increasing, leveling and decreasing trends detected with increasing grazing intensity. Major factors affecting CH4 fluxes included vegetation traits, soil moisture, and soil nitrogen content, with the soil NH4+-N content assuming the most important role. However, predominant factors regulating interannual changes in CH4 uptake were rainfall, belowground biomass, and soil nitrogen regime. Conclusions. The steppe ecosystem acted as a CH4 sink, irrespective of stocking rate and year. However, light grazing can be the threshold grazing intensity in terms of both the CH4 uptake potential and primary production in this steppe ecosystem. Our findings have important implications for further understanding magnitudes and regulations of CH4 uptake in grassland soils worldwide.