Yanben Han

The effect of solar activity on the annual precipitation in the Beijing area

Using continuous wavelet transform, we examine the relationship between solar activity and the annual precipitation in the Beijing area. The results indicate that the annual precipitation is closely related to the variation of sunspot numbers, and that solar activity probably plays an important role in influencing the precipitation on land.

Short-term period variation of relative sunspot numbers

We use wavelet transform to analyze the daily relative sunspot number series over solar cycles 10–23. The characteristics of some of the periods shorter than ~600-day are discussed. The results exhibit not only the variation of some short periods in the 14 solar cycles but also the characteristics and differences around solar peaks and valley years. The short periodic components with larger amplitude such as ~27, ~150 and ~360-day are obvious in some solar cycles, all of them are time-variable, also their lengths and amplitudes are variable and intermittent in time. The variable characteristics of the periods are rather different in different solar cycles.

Atmospheric Excitation of Time Variable Length-of-Day on Seasonal Scales ∗

We use the method of wavelet transform to analyze the time series of the Earths rotation rate of the EOP (IERS) C04. The result shows that the seasonal (annual and semiannual) variation of the length-of-day (LOD) has temporal variability in its period length and amplitude. During 1965.0–2001.0, the periods of the semiannual and annual components varied mainly from 175-day to 190-day and from 360-day to 370-day, respectively; while their amplitudes varied by more than 0.2 ms and 0.1 ms, respectively. Analyzing the axial component of atmospheric angular momentum (AAM) during this period, we have found that time-variations of period lengths and amplitudes also exist in the seasonal oscillations of the axial AAM and are in good consistency with those of the seasonal LOD change. The time variation of the axial AAM can explain largely the change of the LOD on seasonal scales.

Atmospheric and Oceanic Excitations to LOD Change on Quasi-biennial Time Scales

We use wavelet transform to study the time series of the Earths rotation rate (length-of-day, LOD), the axial components of atmospheric angular momentum (AAM) and oceanic angular momentum (OAM) in the period 1962–2005, and discuss the quasi-biennial oscillations (QBO) of LOD change. The results show that the QBO of LOD change varies remarkably in amplitude and phase. It was weak before 1978, then became much stronger and reached maximum values during the strong El Nino events in around 1983 and 1997. Results from analyzing the axial AAM indicate that the QBO signals in axial AAM are extremely consistent with the QBOs of LOD change. During 1963–2003, the QBO variance in the axial AAM can explain about 99.0% of that of the LOD, in other words, all QBO signals of LOD change are almost excited by the axial AAM, while the weak QBO signals of the axial OAM are quite different from those of the LOD and the axial AAM in both time-dependent characteristics and magnitudes. The combined effects of the axial AAM and OAM can explain about 99.1% of the variance of QBO in LOD change during this period.

Historical Dataset Reconstruction and a Prediction Method of Solar 10.7cm Radio Flux

We reconstruct the developing history of solar 10.7cm radio flux (F10.7) since 1848, based on the yearly sunspot number and the variations. A relationship between the maximum and the linear regression slope of the first 3 years starting from minimum of the solar cycle is considered. We put forward a method of predicting the maximum of F10.7 by means of the slope-maximum relationship. Running tests for cycles 19 to 23 indicate that the method can properly predict the peak of F10.7.

A method to predict amplitude and date of maximum sunspot number

A method to predict the amplitude and date of the maximum sunspot number is introduced. The regression analysis of the relationship between the variation rate of monthly sunspot numbers in the initial stage of solar cycles and both of the maximum and the time-length of ascending period of the cycle showed that they are closely correlative. In general, the maximum will be larger and the ascending period will be shorter when the rate is larger. The rate of sunspot numbers in the initial 2 years of the 23rd cycle is thus analyzed based on these grounds and the maximum of the cycle is predicted. For the smoothed monthly sunspot numbers, the maximum will be about 139.2 ±18.8 and the time-length of ascending period will be about 3.31±0.42 years, that is to say, the maximum will appear around the spring of the year 2000. For the mean monthly ones, the maximum will be near 170.1±22.9 and the time-length of ascending period will be about 3.42 ±0.46 years, that is to say, the appearing date of the maximum will be later.

Solar energetic particle event of 2005 January 20: Release times and possible sources

Based on cosmic ray data obtained by neutron monitors at the Earths surface, and data on near-relativistic electrons measured by the WIND satellite, as well as on solar X-ray and radio burst data, the solar energetic particle (SEP) event of 2005 January 20 is studied. The results show that this event is a mixed event where the flare is dominant in the acceleration of the SEPs, the interplanetary shock accelerates mainly solar protons with energies below 130 MeV, while the relativistic protons are only accelerated by the solar flare. The interplanetary shock had an obvious acceleration effect on relativistic electrons with energies greater than 2 MeV. It was found that the solar release time for the relativistic protons was about 06:41 UT, while that for the near-relativistic electrons was about 06:39 UT. The latter turned out to be about 2 min later than the onset time of the interplanetary type III burst.

“Double dawn”eclipse and the rotational variation of the earth

A record of “double dawn” at State Zheng in the first year of the reign of King Yi in Western Zhou Dynasty in the chronicle “Bamboo Annals” (Zhushu Jinian) is discussed. We think that it may be a record of an annular solar eclipse happening in 899 BC. The record and the †T, which describes the secular variation of the earth’s rotation, are analyzed and discussed.

Test on the predictions of solar cycle using the rising rate of monthly sunspot number

The period of about 11-year is the most significant quasi-periodic component in solar activity. The amplitude of the period is often used to indicate the activity intensity of a solar cycle. Solar activity affects the space weather, spaceflight and Earth climate. Solar physical scientists pay attention to studies of solar activity, and some geo-scientists are interested in the relationship between solar activity and some geophysical phenomena. So prediction of relative number of sunspots (SSN) has attracted the attention of many scientists in order to understand the activity of new solar cycle and study the variation of geophysical phenomena. Some prediction methods were used to predict the amplitude of the coming solar cycle, especially for the prediction of the amplitudes for solar cycles 22–24. The results show that only about 1/3 are better in many predictions, the relative predicted error is less than 20%. So it is still difficult to accurately predict the maximum of SSN. In 2000, the amplitude for solar cycle 23 was predicted using rising rate of SSN in earlier ascending phase of cycles by Han. The subsequent compare of actual maximum and prediction showed that the relative predicted error is about 15.2%. The motivation of this paper is to simply introduce how to use the method to predict the solar cycle 23, test the simulation prediction for solar cycle 24 using the new version SSN series (V2.0), and compare the results with those obtained by other researchers using different methods, in order to proof-test the ability of the method. The method uses regression analysis to calculate the rising rates of monthly smoothed SSN in initial stage of past solar cycles, and then calculate the quantitative relationship between the rising rates and corresponding maximums of the solar cycles using regression analysis again. Some tests show that they have high correlation when we use SSN in 1–24 months of initial stage of past solar cycles. Then we calculate the rising rate and use the rate to predict the amplitude of the coming solar cycle. The paper focuses on the simulative predictions of maximum amplitude for 22–24 cycles using the method and V2.0 SSN series. For the 3 cycles, predicted values of maximum amplitudes are 234.9, 191.9 and 134.1, they are in good agreement with the actual values, 212.5, 180.3, 116.4, and the relative prediction errors are about 10.6%, 6.4% and 15.2%, respectively. This shows that the prediction method has a certain application value possibly. Anyway, the studies of solar activity characteristics should be continually enhanced, as well as the studies of methods for predicting the solar activity in the future, to select relatively better prediction methods and improve the level of solar activity prediction. Meanwhile, the rising rate is obtained by the SSN in 1–24 months of the initial stage of a cycle, for the monthly smoothed SSN series, only at the 31st month after the beginning of a cycle can get smoothed values of 24 months and then to calculate rising rate. However, the rising stage is about 4–6 a, which makes the predicted leading time to be not long enough. The authors are considering the improvement of this method and to do more tests.