Sub-seasonal variations of the tropical storm track in the western north Pacific

With 20-year (1975-94) climatological data, we demonstrate that the tropical storm track over the western North Pacific (0° - 40°N, 100 - 180°E) exhibits prominent sub-seasonal variations on a time scale of about 40 days from May to November. The storm track variability is regulated by the conspicuous Climatological Intra Seasonal Oscillation (CISO) in the strength of the western North Pacific summer monsoon and the associated position of the western Pacific Sub-tropical High. The CISO cycle regulates the number of tropical storm formation during the Pre-Onset and Withdraw Cycles but not during the Onset and Peak Monsoon Cycles (from mid-June to mid-September).

Recent Changes in Temperature and Precipitation of the Summer and Autumn Seasons over Fujian Province, China

Based on the observation data of daily temperature and precipitation in summer and autumn of 68 representative meteorological stations in Fujian Province from 1971 to 2018, using the climate Tendency Rate, Mann-Kendall trend test, Morlet wavelet analysis and other methods, this paper analyzes the variation trends of air temperature and annual precipitation and the wavelet periodic variation characteristics of annual precipitation time series in summer and autumn of Fujian Province over a period of approximately 48 years. The results show that over the approximately 48 years, the temperature and precipitation in summer and autumn in Fujian showed an obvious upward trend, which had a mutation around 2000, but the mutation time was different, and the precipitation was slightly earlier. The annual temperature and precipitation in summer and autumn experienced three oscillations on the 28a scale. In the 28a time scale of summer autumn seasonal oscillation, there are three negative centers and two positive centers. According to the characteristics of annual average temperature and annual precipitation in the first major cycle, the annual precipitation in summer and autumn will continue to increase in the future.

Validation of the ESA CCI+SSS products

<div> <p><span>The </span><span>European Space Agency (ESA) Climate Change Initiative (CCI+) for Sea Surface Salinity (CCI+SSS) project aims at generating long-term, improved, calibrated global SSS fields from space. </span>The project started in mid-2018 and in its second year (version 2) has produced a 10-year dataset (2010-2019) from the three available L-band radiometer satellites (SMOS: Soil Moisture and Ocean Salinity; Aquarius; SMAP: Soil Moisture Active Passive) and validated it against in situ references (Argo and ISAS: In Situ Analysis System). The comparisons with in situ ground truth indicate much better performances than the ones obtained with a single satellite data product, with global precision against in situ references of 0.15 pss. CCI SSS version 2 products show similar performance than version 1 but is one year longer. There is a very good agreement between the CCI dataset and references, including long-term stability, with differences within +-0.05 pss for global ocean within [40°S-20°N]. At higher latitude, we observe seasonal oscillation of the CCI SSS difference against references. The uncertainty provided in the CCI SSS product are in good agreement with observations (within +-25%).</p> </div>

Accumulated Effect of Intra-Seasonal Oscillation Convections over the Tropical Western North Pacific on the Meridional Location of Western Pacific Subtropical High

An extreme northward displacement of the western Pacific subtropical high (WPSH) was detected during the boreal mid-late summer (July-August) of 2018, bringing record-breaking heat waves over northern East Asia. Negative sea surface temperature (SST) anomalies in the northern India Ocean (NIO) are usually accompanied with a northward shift of the WPSH. However, no prominent NIO SST anomalies were observed during the 2018 boreal summer. It is found that this extreme northward-shifted WPSH event is largely attributed to the accumulated effect of intra-seasonal oscillation (ISO) convection anomalies over the tropical western North Pacific (WNP). The accumulated effect on the WPSH meridional location is further supported by their significant correlation based on the data since 1979. While the relationship between the NIO SST anomalies and WPSH meridional location has substantially weakened since the late 1990s, the accumulated effect of the tropical WNP ISO convections keeps playing a crucial role in modulating the WPSH meridional displacement. The active WNP ISO activities can stimulates a poleward propagating Rossby wave train, which favors a northward shift of the WPSH. Our results suggest that the accumulated effect of the tropical WNP ISO convections should be considered when predicting the WPSH during the boreal mid-late summer season.

Intra-seasonal Oscillation of Abyssal Currents in the Middle East Pacific Ocean

<p>In this work, the intra-seasonal oscillation of the abyssal currents in the Middle East Pacific Ocean is investigated using direct observations from ADCP instruments, which are mounted on a subsurface mooring deployed at 154oW，10oN. The observation shows that the intra-seasonal (20-100 days) oscillation part of the kinetic energy accounts for more than 40% of the low-frequency flow kinetic energy between 200~2000m, while accounts for more than 50% under 2000m; the intra-seasonal oscillation of meridional flow is more obvious than that of zonal flow. The meridional velocity in the upper layer (100-1000m) shows an oscillation at periods of 50~90 days, which is most obvious at the depth of 500m; from 200m to the bottom layer currents shows an synchronous oscillation at a period of 30 days lasting for several months, and the oscillation signal is the strongest in the deep layer (4600m); The correlation is good between the 20~40 day band passed meridional current at the bottom layer and that of the geostrophic current. The observed temperature of 4000m and 5000m also shows similar characteristics of 30 days period oscillation, which has good correlation to the sea level height. The reanalysis data shows the 30 days oscillation of the abyssal currents is propagated from west to east at a speed of about 0.29m/s while the 40~100 day oscillation is propagated at a speed of about 0.1m/s; the intensity of the intra-seasonal oscillation has obvious interannual variations, which may be related to the change of the eddy energy of the sea surface.</p>