CORRELATION OF GLOBAL CLOUDINESS WITH BURSTS IN TOTAL SOLAR IRRADIANCE

Transcription

1 CORRELATION OF GLOBAL CLOUDINESS WITH BURSTS IN TOTAL SOLAR IRRADIANCE S.V. Avakyan 1,2,3, N.A.Voronin 1, S.S. Kavtrev 3 1 All-Russian Scientific Center S.I. Vavilov State Optical Institute, St. Petersburg, Russia, avak2@mail.ru; 2 St. Petersburg State Polytechnical University, St. Petersburg, Russia; 3 Russian State Scientific Center for Robotics and Technical Cybernetics, St. Petersburg, Russia Abstract. Studies of the response of the global cloudiness to solar forcing are essential for meteorological forecasting. From ISCCP data we found positive reaction of two types of cloudiness to bursts in the total solar irradiance on the month scale. The best correlation with TSI is displayed by upper cloudiness (in 93% cases against 81% for the total cloudiness). This result is consistent with our idea that in the times of solar forcing the upper cloudiness is generated basically as a result of acceleration of water vapour clusterization due to the increase in microwave fluxes from ionosphere (this mechanism was suggested by us previously). Another manifestation of the response of parameters of global cloudiness to solar forcing was revealed in trends observed in the total and upper cloudiness. Within , i.e. for about 80% of the total time of the measurements, these trends displayed the same direction, and were consistent with the hypothesis of the prevalence of secular variations in solar-geomagnetic activity at the present stage of global warming. Corresponding parameters of solar-geomagnetic activity are the number of large solar flares and principal geomagnetic storms accompanied with the increase in fluxes of ionizing solar radiation and corpuscles resulting in supplementary microwave emission from the terrestrial ionosphere. 1. Studies of the response of characteristics of global cloudiness to variations of solar activity present considerable scientific and practical interest. Given the revealed influence of rapid variations in the solar constant (TSI) on the formation of clouds in the global scale, data on the solar geomagnetic activity can be used in weather and climatic forecasting, in particular, for middle- and long-term weather forecasts. Here, we describe the stable positive reaction to TSI bursts for two types of cloudiness (total and high), derived from ISCCP global data for the years averaged over months. The highest positive correlation is obtained for the upper cloudiness (UC) averaged over months (93% of the cases), while for the total cloudiness (TC) the correlation is lower (81% -- Fig. 1). Within the interval , 32 cases of coincidence of all three parameters (TSI, TC and UC) were found, 8 cases for TSI and UC, and 3 cases for TSI and TC. No significant correlation with the lower cloudiness was detected (Fig. 3), and only 50% coincidence was seen in the case of middle cloudiness (Fig. 2). Fig. 1. Comparison between variations of the global total and upper cloudiness (ISCCP/GISS/NASA data) and those of the solar constant (Total Solar Irradiance - TSI). 211

2 Fig. 2. Comparison between variations of the global middle cloudiness (ISCCP/GISS/NASA data) and those of the solar constant (TSI). Fig. 3. Comparison between variations of the global lower cloudiness (ISCCP/GISS/NASA data) and those of the solar constant (TSI). These results indicate the decisive contribution of microwave radiation from the ionosphere to the formation of primarily upper (as a rule, cirrus) optically thin cloudiness. Thereby, it is indeed UC that contributes mostly into the correlation between TSI and TC; this is consistent with the radio-optical mechanism of solarto-atmosphere correlations previously suggested by The S.I. Vavilov Optical Institute. It determines the speed is increased clustering of water vapor due to increasing ionospheric microwave radiation during periods of solar forcing in the formation of condensation-cluster haze in the troposphere, which develops later in optically thin, usually the upper (cirrus) cloudiness [Avakyan, 2013]. 2. The detected effect of coincidence of TSI bursts and peaks of the total cloudiness (averaged over months) may be applied to forecasting regional anomalies in the air temperature. We are planning to use statistical data of: - evolution of the faculae activity in the solar spectrum; - correlation between the average long-term variability of cloudiness and temperature anomalies (known for 5-day intervals through a total year) in a given region. 3. We also compared the type and magnitude of trends in TC and UC, and noted that: - for about 80% of the time, they are of the same direction; - variations in the rate of this direction is consistent with the hypothesis of the domination of secular variations of solar-geomagnetic activity at the current stage of the global warming. The above is seen in Fig.1, which presents the trends for TC and UC: (1) the interval until the years 1985/87, when both the solar and geomagnetic activity grew in the secular cycle; (2) the interval 1987 to 2000, when the solar electromagnetic (since 1985) and corpuscular activity was falling; (3) the interval 2000 to 2003, when the geomagnetic activity kept growing; this growth lasted from the 19-th century to the absolute maximum in 2003; 212

3 (4) a new decrease since early 2004, related to the total decline of the solar-geomagnetic activity in the current secular cycle. For the upper cloudiness, the first three trends are the same; from the beginning of 2004, instead of the decline, a growth is detected, which we relate to previously registered increase in the flux of the cosmic rays, up to the maximum reached in September, The presented evidences of the dependence of the global cloudiness on the level of solar-geomagnetic activity in the decades of the observed maximum of the current secular cycle confirm the conclusion [Avakyan, 2013] that the solar activity is a natural driving force of the current stage of the global warming. 4. Besides, we analyzed the comparison between time variations of the total column atmospheric water vapor (TCAWV) and the occurrence of cloudiness in different layers, as well as the column atmospheric water vapor in two altitude zones with the pressure mb and mb. For TCAWV, we found coincidence in more than 92 % of the cases, i.e. the total synchronicity of the variations (derived from overlapping of the maxima and minima see Fig. 4, 5) of all three parameters, and also good similarity of their trends. Fig. 4. Comparison between TCAWV time variations and column atmospheric water vapor in the altitude zone with the pressure mb Fig. 5. Comparison between TCAWV time variations and column atmospheric water vapor in the alttiude zone with the pressure mb From the comparison of TCAWV variations with the lower cloudiness (LC), we derived that, despite the fact that their minima coincide in 86 % cases, the maximum of LC usually precedes that of TCAWV. This is apparently a manifestation of the effect known from model calculations, when along with the increase in the upper level cloudiness, LC decreases due to decay of descending vertical flows [Borisenkov et al., 1989]. This is what results in earlier appearance of LC maxima in 88% cases. Consequently, this process is not related directly to water vapor clusterization, and it cannot be considered directly controlled by the level of the solar activity, either. Clearly, this process is not determined by solar forcing in a direct way. The values of TCAWV and middle-level cloudiness (MC) virtually totally anti-correlate, i.e. the MC is generated through water vapor clusterization. 213

4 For high cloudiness (UC), the correlation is seen in 62 % cases; it is obvious that the water vapor clusterization also occurs here. The contribution of ion formation under the action of galactic cosmic rays is substantial, since it is from this altitude zone that the ionization rate becomes appreciable. Fig. 6. Comparison between TCAWV time variations and lower cloudiness (LC). Fig. 7. Comparison between TCAWV time variations and middle cloudiness (MC). Fig. 8. Comparison between TCAWV time variations and upper cloudiness (UC). 214

5 Fig. 9. TCAWV time variation at the altitude 1600 m, Tien-Shan (Kyrghyzia). Fig. 10. TCAWV time variation in Texas (USA). 5. The comparison between time variations of TCAWV at the heights of 1600 m (Tien-Shan, Kyrghyzia, [Aref ev et al., 2006]) and 500 m (Texas, USA, [Mims et al., 2011]), with the correlation 0,765 within the interval of synchronous measurements 1990 to 2005, presented in Figs 9 and 10, taking into account the anticorrelation between trends in cloudiness and in TCAWV, confirm the global spread of their (TCAWV) reaction to variations of solar-geomagnetic activity. 6. In the study [Pokrovskii, 2012], a striking inconsistency is noted between the decrease in the global cloudiness with the simultaneous increase in the temperature of the ocean surface (apparently accompanied with the increase in vaporization from the surface of water) and the existing mechanisms of cloud formation. This effect was detected in ISCCP experiment and observed up to the interval 2005/9. Our results indicate that the evolution of the global cloudiness is basically driven by the variations of the solar-geomagnetic activity, while TCAWV remains a second-order factor in the formation of clouds. In fact, TCAWV does not specify the formation of cloudiness in the global scale, since the abundance of water vapor is, as a rule, sufficient for that. Within the framework of the radio-optical mechanism of solar-terrestrial links, which we previously developed in The S.I. Vavilov Optical Institute, the microwave flux from the ionosphere is another important controlling factor of the cluster condensation in the troposphere. Therefore, the phenomenon presented in [Pokpovskii, 2012] also confirms the idea of domination of solar-geomagnetic activity in the condensation-cluster mechanism of the formation of cloudiness, and subsequently in the control over weather and climatic parameters [Avakyan, 2013]. References Aref ev, V.N., F.V. Kashin, V.K. Semenov, R.M. Akimenko, N.E. Kamenogradskii, N.I. Sizov, V.P. Sinyakov, L.B. Upenek, V.P. Ustinov (2006), Water vapor in the atmosphere over the northern Tien Shan. Izvestiya, Atmospheric and Oceanic Physics, 42 (6), Avakyan, S.V. (2013), The role of solar activity in global warming. Herald of the Russian Academy of Sciences, 83 (3),

6 Borisenkov, E.P., T.A. Bazlova, and L.N. Efimova (1989), Cirrus and its influence at the atmospheric processes, Gidrometeoizdat, Leningrad, 119 pp. Mims, F.M. III, L.H. Chambers, and D.R. Brooks (2011), Measuring Total Column Water Vapor by Pointing an Infrared Thermometer at the Sky. Bull. Amer. Meteor. Soc., 92, Pokrovskii, O.M. (2012), Climatology of clouds on the results of the international satellite project. Trudy A.I. Voeikov GGO, 565, (In Russian). 216