Research On Global Atmospheric And Oceanic Thermal Properties Based On Theory Of Abrupt Change Process

Climate system is a complex nonlinear system, and its time series is not constant. Climate sequence always has a transition from one state to another, which is called abrupt climate change.In the previous research on abrupt climate change, the abrupt change event was considered as a“point” by judging the difference between two states before and after the “point” to identify the abrupt change. If the abrupt climate change was defined as one “point”, its dynamic evolution process would be vanished, thus the abrupt climate change can not be predicted in many climate models. When the real climate system changes abruptly, it has a transition process including the system deviating from the original stable state, during the transition process between two states,and the system arriving to another state. Research on abrupt climate change process forces on the abrupt change event to analyze the transition process where the system staying, and it is different from the traditional study of abrupt change “point”.In present paper, an analysis method of abrupt climate change process is proposed to study the transition process between two states, and the method is created from a nonlinear biological model which can get the abrupt climate change process from a real climate sequence. The transition process are expressed by a group of parameters, including “start state” parameter which is the state before abrupt change, “end state” parameter which is after abrupt change, “abrupt change rate” parameter which is the rate from the “start state” to the “end state”, and “stability parameter” which deputies whether the system is stable during the transition process. “Abrupt change amplitude” is the difference between “start state” and “end state”, and “persist time”represent the period from “start state” and “end state”. Through theoretical derivation and verification of the real climate sequence, an important relationship among the parameters reveals that the relationship between the “abrupt change rate” and the “stability parameter” is linear, but that between the “abrupt change rate” and the “abrupt change amplitude” is parabolic. The relation exposed a phenomenon that the climate change happened abruptly with a large amplitude.By analyzing the parameters, the abrupt climate change process is reappeared. Considering that the global temperature raised in the past decades, and the temperature time sequence were detected several times of abrupt climate changes, this method is applied to the global airtemperature and sea surface temperature to study the climate change process of sea-air system.According to the huge ocean heat content, the characters of ocean heat content are studied to expose the cause of climate change. Based on the analysis method of abrupt climate change process, a prediction method is created to predict the “end state” of the climate index.(1)The analysis method of abrupt climate change process is proposed and the transition process is reappeared. Based on the detection method, “start state” and “end state” are extracted from a real climate sequence. When the “persist time” is unknown, a sub-sequence is intercepted from the original time sequence to identify the “start state” and “end state”. By moving the sub-sequence on the entire time sequence, a series of “start states” and “end states” parameters are obtained to build a scatter plot, which is called “Start-End states” phase diagram. The phase diagram can be used to show the transition process, the continuous vertical line of the scatter lot means that the system is deviating from the original state, the continuous horizontal line is that the system is arriving to a new state, and the continuous oblique line represents that the system is staying the process between two states. The application on the ideal time sequence and the real climate sequence indicates that the method is appropriate and effective.(2)Research on the abrupt climate change and its transition process of global air temperature. By applying the detection method to the reanalysis data to study the transition process of the global temperature change process, three periods(1987-1992, 1997-2000 and2000-2004) of abrupt changes are identified during the short rang 1979-2012(NCEP-2) and three periods(the end of 1950s/1970s/1990s) of the long rang 1948-2012(NCEP-1) are also detected.The different between the two results of long rang sequence and short rand sequence indicates that the threshold of the abrupt change is relative to the time-scale of the sequence. The abrupt change of 1987-1992 was not detected as one abrupt change in long rang sequence, because it had a small threshold. And the abrupt changes of period 1997-2000 and 2000-2004 were considered as one abrupt change happened in the end of 1990 s. The abrupt change process of 500 h Pa temperature indicates that the temperature of 1986-1994 decreases 0.33℃, while the temperatures of1956-1959, 1970-1979 and 1994-2004 increase 0.37, 0.16 and 0.23℃ respectively. The abrupt change amplitudes gradually decrease from high latitude to low latitude, and it’s becoming bigger than bigger with global warming. Besides, the stability parameter suggests that the system becomes unstable when it’s during the transition process.(3)Research on the abrupt climate change and its transition process of sea surface temperature. Based on the detection method, the global sea surface temperature(SST) over the past century has been studied and several times of abrupt changes(including three moments 1878,1942, 1976 and two periods 1890-1920, 1990-2010) are detected. The abrupt changes before2000 s occurred mainly in Indian ocean, and in 20 century, the abrupt changes happened mainly in the Pacific, while the abrupt changes occurred in polar regions in the end of 20 century. It’s noticeable that the persist time experienced a long period(5-10a) before 1942, and after that the duration was shorting(it was about 5a, and the duration of 1976 was 5-8a). The temperatures of abrupt change mainly decreased before 1942, while it increased after 1942.(4)Research on the ocean heat content to study the mechanism of abrupt climate change.Based on the temperature and salinity, the studying of the ocean heat content in different depth shows that shallow layer’s(above 80m) heat content in the low latitude region is higher than that in the middle latitude region, and the middle layer’s(below 80 m and above 380m) heat content in middle latitudes are higher than that in lower latitudes. The heat content of deeper ocean in Indian ocean and Atlantic ocean are much higher than that in the Pacific. From the angle of period, the trend of heat content before 1970 is negative and it is positive after 1970. The ocean heat’s time scales of different depth from the surface layer to the bottom are changed from high frequency to low frequency because of the solar radiation. And the time scales of Indian ocean, Pacific ocean and Atlantic ocean are changed from high frequency to low frequency due to the difference among their sea basins. The heat transfer among the three oceans has a inter-decadal abrupt turning in1980 s, which more heat transferred to Atlantic ocean from Indian ocean and Pacific ocean. And more heat transferring from the surface layer to the bottom layer might lead to the global climate change.(5)An index of the abrupt climate changes of Coupled Air-sea System based on the sea surface temperature and salinity of tropical Pacific. By studying the sea surface temperature,sea level pressure, horizontal wind, vertical wind, and sea surface precipitation, it indicates when the sea surface temperature raises, the sea level pressure and the vertical wind speed are becoming large in the same place, and the precipitation gets more, which leads the sea surface salinity decreasing. It’s noticeable that the increasing of the temperature leads to the decreasing of salinity.Both the temperature and the salinity has a linear relationship to the heat content, which means when the temperature and the salinity increase the heat content increases too. Thus the process is negative feedback. The circulation of the sea surface temperature and salinity can be an index of the abrupt climate changes of Coupled Air-sea System. The research indicates that the cycle period is about 3-8a, and the period of each circulation is shorting with global warming. Besides, the circulations of the two periods( the beginning of 1970 s and the end of 1990s) with abrupt changes are different from the other periods, which indicates that the circulation of temperature and salinity is the index of the abrupt climate change.(6)The prediction of the PDO index’s abrupt change. According to the quantitativerelationship among the parameters of “abrupt change rate”, “stability parameter”, “abrupt change amplitude”, a prediction of abrupt change is created. By identifying the “start state” before the abrupt change, “the abrupt change rate” through the trend of climate change, and having the“stability parameter” obtaining from the historical data, the “end state” can be calculated based on the quantitative relationship. The prediction of the Pacific Decadal Oscillation index shows that the time series start to change in 2011 and the end before 2017.