Effect of Decadal Changes in Air-Sea Interaction on the Climate Mean State over the Tropical Pacific

Collaboration of interannual variabilities and the climate mean state determines the type of E1 Nifio. Recent studies highlight the impact of a La Nifia-like mean state change, which acts to suppress the convection and low-level convergence over the central Pacific, on the predominance of central Pacific （CP） E1 Nifio in the most recent decade. However, how interannual variabilities affect the climate mean state has been less thoroughly investigated. Using a linear shallow-water model, the ef- fect of decadal changes of air-sea interaction on the two types of El Nifio and the climate mean state over the tropical Pacific is examined. It is demonstrated that the predominance of the eastem Pacific （EP） and CP E1 Nino is dominated mainly by relationships between anomalous wind stresses and sea surface temperature （SST）. Furthermore, changes between air-sea interactions from 1980-98 to 1999-2011 prompted the generation of the La Ninalike pattern, which is similar to the background change in the most recent decade.

Mean Sea Level Changes near Weizhou Island from 1969 to 2010

Tidal data from Weizhou, Zhapo, and Shanwei stations between 1969 and 2010 and from five gauging stations in the western Pacific Ocean provided by PSMSL, and the global mean sea level data recorded between December 1992 and December 2010 by TOPEX and Jason satellites were compiled and analyzed. The results show that the perennial mean sea level near Weizhou Island is 211.7 cm(relative to the water gauge zero), and the relative mean sea level rising rate is 2.2 mm yr-1 from 1969 to 2010, which is consistent with the relative mean sea level rising rate recorded at other gauging stations in the western Pacific regions and with the global mean sea level rising rate. The absolute mean sea level rising rate at Weizhou Island is 3.0 mm yr-1 from 1993 to 2010, also conforming with the global mean sea level rising rate(3.1±0.4 mm yr-1) during the same time period. The highest annual tide level at Weizhou Island has a rising rate of 4.6 mm yr-1 and shows a 20-year quasi-periodic variation from 1966 to 2010. The primary cause of the mean sea level rising is global warming.

Quantifying the Mean Sea Level Change at the Gulf of Finland Coast Caused by the Realistic Portion of the Global Warming Forcing

Quantifying the coastal mean sea level change causing by the winter positive phase of the North Atlantic oscillation index NAO＋ at the Gulf of Finland coast is of high priority for detecting and predicting the global warming impact in this region. Both boreal winter months and season of three long-term data station series of the coastal mean sea levels and the NAO indices were linked for two cases, i.e.： different periods and the 1977-1994 period. This study is dedicated to： （1） Detecting the exclusive impacts of the NAO＋; （2） Estimating the significant standard bivariate linear regression models; （3） Calculating the climatic linear trend coefficient by using three methods （OLS, GLS, Theil-Sen）; （4） Correcting the mean sea level series anomalies by using the significant linear regression equations as a function of NAO＋ anomalies, over the period 1977-1994; （5） Calculating the realistic linear trend caused as a function of NAO＋ for period 1977-1994 in the context of the realistic portion of the global warming. The results reveal that, the NAO＋ manifests their impacts on the coastal mean sea levels and its contribution in the configured linear trends. The realistic linear changes have detected and predicted. The Gulf of Finland coast showed the wannest regions in the context of the realistic portion of the global warming during the winters of the period 1977-1994.

The Influence of Weather and Climate Variability on Groundwater Quality in Zanzibar

Climate change and variability have been inducing a broad spectrum of impacts on the environment and natural resources including groundwater resources. The study aimed at assessing the influence of weather, climate variability, and changes on the quality of groundwater resources in Zanzibar. The study used the climate datasets including rainfall (RF), Maximum and Minimum Temperature (Tmax and Tmin), the records acquired from Tanzania Meteorological Authority (TMA) Zanzibar office for 30 (1989-2019) and 10 (2010-2019) years periods. Also, the Zanzibar Water Authority (ZAWA) monthly records of Total Dissolved Solids (TDS), Electrical Conductivity (EC), and Ground Water Temperature (GWT) were used. Interpolation techniques were used for controlling outliers and missing datasets. Indeed, correlation, trend, and time series analyses were used to show the relationship between climate and water quality parameters. However, simple statistical analyses including mean, percentage changes, and contributions to the annual and seasonal mean were calculated. Moreover, t and paired t-tests were used to show the significant changes in the mean of the variables for two defined periods of 2011-2015 and 2016-2020 at p ≤ 0.05. Results revealed that seasonal variability of groundwater quality from March to May (MAM) has shown a significant change in trends ranging from 0.1 to 2.8 mm/L/yr, 0.1 to 2.8 μS/cm/yr, and 0.1 to 2.0℃/yr for TDS, EC, and GWT, respectively. The changes in climate parameters were 0.1 to 2.4 mm/yr, 0.2 to 1.3℃/yr and 0.1 to 2.5℃/yr in RF, Tmax, and Tmin, respectively. From October to December (OND) changes in groundwater parameters ranged from 0.2 to 2.5 mm/L/yr 0.1 to 2.9 μS/cm/yr, and 0.1 to 2.1℃/yr for TDS, EC, and GWT, whereas RF, Tmax, and Tmin changed from 0.3 to 1.8 mm/yr, 0.2 to 1.9℃/yr and 0.2 to 2.0℃/yr, respectively. Moreover, the study has shown strong correlations between climate and water quality parameters in MAM and OND. Besides, the paired correlation has shown significant changes in all parameters except the rainfall. Conclusively, the study has shown a strong influence of climate variability on the quality of groundwater in Zanzibar, and calls for more studies to extrapolate these results throughout Tanzania.

A New Method for Determining Threshold in Using PGCEVD to Calculate Return Values of Typhoon Wave Height

In using the PGCEVD （Poisson-Gumbel Compound Extreme Value Distribution） model to calculate return values of typhoon wave height, the quantitative selection of the threshold has blocked its application. By analyzing the principle of the threshold selection of PGCEVD model and in combination of the change point statistical methods, this paper proposes a new method for quantitative calculation of the threshold in PGCEVD model. Eleven samples from five engineering points in several coastal waters of Guangdong and Hainan, China, are calculated and analyzed by using PGCEVD model and the traditional Pearson type III distribution （P-III） model, respectively. By comparing the results of the two models, it is shown that the new method of selecting the optimal threshold is feasible. PGCEVD model has more stable results than that of P-III model and can be used for the return wave height in every direction.

Intraseasonal variability of summer monsoon rainfall over the lower reaches of the Yangtze River basin

This work investigates the boreal-summer intraseasonal variability(ISV)of the precipitation over the lower reaches of the Yangtze River basin(LYRB)during 1979–2016,based on daily Climate Prediction Center global precipitation data.The ISV of the summer monsoon rainfall over the LYRB is mainly dominated by the lower-frequency 12–20-day variability and the higher-frequency 8–12-day variability.The lower-frequency variability is found to be related to the northwestwardpropagating quasi-biweekly oscillation(QBWO)over the western North Pacific spanning the South China Sea(SCS)and Philippine Sea,while the higher-frequency variability is related to the southeastward propagating midlatitude wave train(MLWT).Moreover,not each active QBWO(MLWT)in the SCS(East Asia)can generate ISV components of the precipitation anomaly over the LYRB.The QBWO can change the rainfall significantly with the modulation of mean state precipitation,while the quasi-11-day mode mainly depends on the intensity of the MLWT rather than the mean precipitation change.These findings should enrich our understanding of the ISV of the East Asian summer monsoon and improve its predictability.

Influence of Climate on Soil Organic Carbon in Chinese Paddy Soils

Soil organic carbon(SOC) is a major component of the global carbon cycle and has a potentially large impact on the greenhouse effect. Paddy soils are important agricultural soils worldwide, especially in Asia. Thus, a better understanding of the relationship between SOC of paddy soils and climate variables is crucial to a robust understanding of the potential effect of climate change on the global carbon cycle. A soil profile data set(n = 1490) from the Second National Soil Survey of China conducted from 1979 to 1994 was used to explore the relationships of SOC density with mean annual temperature(MAT) and mean annual precipitation(MAP) in six soil regions and eight paddy soil subgroups. Results showed that SOC density of paddy soils was negatively correlated with MAT and positively correlated with MAP(P < 0.01). The relationships of SOC density with MAT and MAP were weak and varied among the six soil regions and eight paddy soil subgroups. A preliminary assessment of the response of SOC in Chinese paddy soils to climate indicated that climate could lead to a 13% SOC loss from paddy soils. Compared to other soil regions, paddy soils in Northern China will potentially more sensitive to climate change over the next several decades. Paddy soils in Middle and Lower Yangtze River Basin could be a potential carbon sink. Reducing the climate impact on paddy soil SOC will mitigate the positive feedback loop between SOC release and global climate change.

RATE OF CONVERGENCE FOR MULTIPLE CHANGEPOINTS ESTIMATION OF MOVING-AVERAGE PROCESSES

In this paper, the least square estimator in the problem of multiple change points estimation is studied. Here, the moving-average processes of ALNQD sequence in the mean shifts are discussed. When the number of change points is known, the rate of convergence of change-points estimation is derived. The result is also true for p-mixing, φ-mixing, a-mixing, associated and negatively associated sequences under suitable conditions.

ON DETECTION OF CHANGE POINTS USING MEAN VECTORS

In this paper,the authors consider the problem of change points within the framework of model selection and propose a procedure for estimating the locations of change points when the number of change points is known.The strong consistency of this procedure is also established. The problem of detecting change points is discussed within the framework of the simultaneous test procedure.The case where the number of change points is unknown will be discussed in another paper.