Effective Solar Radiation Research Articles

Separation of the Asian summer monsoon and local precipitation from stalagmite oxygen isotope records in Eastern China during the last millennium

The Asian summer monsoon (ASM) regulates water vapor and heat transport across the East Asian continent and has a significant impact on patterns of regional precipitation. However, assessment of the long-term association between the monsoon and precipitation in different regions remains difficult due to spatial chronological differences and uncertainties in interpretation of climate proxies. This study provides a novel insight into the interpretation of stalagmite oxygen isotopes (δ18O) records and obtained synchronous ASM index series and precipitation variations in Northern China (NC), Central China (CC), and Southwestern China (SWC) over the last 1134 years (850–1983CE). The results show that the ASM index sequence is consistent with the trend evident in the monsoon intensity records from the region upstream of the water vapor source, which represents the response to the inter-hemispheric temperature dominated by effective solar radiation (ESR). Reconstruction precipitation data were in general agreement with the existing paleo-hydrological records of the regions, confirming the reliability and chronological accuracy of the reconstruction. Correlation analysis highlighted the significant regional heterogeneity in the destabilizing relationship between precipitation and the monsoon over the past millennium in Eastern China at sub-centennial scales. Specifically, the precipitation-monsoon relationships in three regions, NC, CC, and SWC, might be related to the North Atlantic Oscillation (NAO), the position of the intertropical convergence zone (ITCZ), and solar activity, respectively. Moreover, at the millennial scale, a certain positive correlation between precipitation and ASM in NC and SWC was identified, whereas there was a weaker correlation between precipitation and ASM in CC. This study represents an attempt to further interpret the stalagmite δ18O record, which can be generalized to larger and longer time scales.

Modulation of decadal ENSO-like variation by effective solar radiation

Prediction of the Pacific sea surface temperature (SST) anomaly in the coming decades is a challenge as the SST anomaly changes over time due to natural and anthropogenic climate forcing. The climate changes in the mid-1970s and late-1990s were related to the decadal Pacific SST variability. The changes in the mid-1970s were associated with the positive phase of decadal El Niño-Southern Oscillation (ENSO)-like SST variation, and the changes in the late-1990s were related to its negative phase. However, it is not clear whether this decadal SST variability is related to any external forcing. Here, we show that the effective solar radiation (ESR), which includes the net solar radiation and the effects of volcanic eruption, has modulated this decadal ENSO-like oscillation. The eastern Pacific warming (cooling) associated with this decadal ENSO-like oscillation over the past 139 years is significantly related to weak (strong) ESR. The weak ESR with strong volcanic eruption is found to strengthen the El Niño, resulting in an El Niño-like SST anomaly on the decadal time scale. The strong eruptions of the El Chicho’n (1982) and Pinatubo (1991) volcanoes reduced the ESR during the 1980s and 1990s, respectively. The radiation reduction weakened the Walker circulation due to the “ocean thermostat” mechanism that generates eastern Pacific warming associated with a decadal El Niño-like SST anomaly. This mechanism has been confirmed by the millennium run of ECHO-G model, in which the positive eastward gradient of SST over the equatorial Pacific was simulated under the weak ESR forcing on the decadal time scale. We now experience a reversal of the trend in the ESR. The strong solar radiation and lack of strong volcanic eruptions over the past 15 years have resulted in strong ESR, which should enhance the Walker circulation, leading to a La Niña-like SST anomaly.

Assessment of Overall Thermal Transfer Value (OTTV) in Buildings with Inclined Glass Wall

The Ministry of Energy of Thailand promulgated the criteria for computing the Overall Thermal Transfer Values (OTTV) to manage building energy efficiency in 1992. These criteria were improved in 2009 to cover dissimilar heat transfer rates in the daytime and the nighttime for offices, stores and hotels constructed with 0 to 90-degree roofs and walls. However, the assessment of OTTV of buildings with wall inclinations greater than 90 degrees has been excluded with only approximate values being used in the calculation. The objective of this paper, therefore, is to propose a calculation method of Effective Solar Radiation (ESR), a variable in OTTV equation, for office buildings with 105-150 degree wall inclinations, taking into account the effects of ground reflectance values of 0.05, 0.2 and 0.32 for water, grass, and white concrete, respectively. The ESR values for the inclined glass wall were obtained from the slope of linear relationship between the simulated solar heat gain and the glass’s Solar Heat Gain Coefficient (SHGC). The simulated results and the regression analysis showed that the derived ESR values of the vertical wall were compatible with the ESR values in the building energy code (BEC) and the energy used index, similar to that obtained from energy audits. The ESR values decreased by 2.7-37% as the glass wall inclination increased, resulting in a decrease of the OTTV by 2.0-17%. For the high ground reflectance of 0.32 and SHGC of 0.54, the results showed that the OTTVs of the building with inclined walls exceeded 50 W/m2. Therefore, grass and water are recommended for the landscape around energy efficient buildings.

Relationship between effective solar radiation and sap flow process during an entire growing season in Western Mountains of Beijing

In order to explore the relationship between the time processes of solar radiation and sap flow, sap flow velocity (SFV) of Platycladus orientalis and Pinus tabulaeformis, effective solar radiation (ESR) and other environmental factors were synchronously monitored for one year in the Beijing Western Mountains by using a thermal dissipation probe (TDP) system and an automatic weather station. Results showed significant differences between changes in diurnal characteristics of ESR and sap flow in sunny days during three seasons. Starting times of sap flow occurred generally 1.5–3 hours later than those of solar radiation and there were small differences between Platycladus orientalis and Pinus tabulaeformis. But peak times and stopping times of sap flow varied considerably with large contrasts in ESR. The duration of sap flow showed clear differences among the seasons owing to the variable rhythms of climate factors in Beijing. Fluctuation amplitude in the duration of sap flow remained relatively stable during the autumn but changed greatly during spring and summer. Changes in diurnal sap flow velocity of both Platycladus orientalis and Pinus tabulaeformis were about 0–3 hours later than those of ESR but with the same configuration. The start of sap flow was mainly induced by the sudden intensification of ESR (sunrise effect). Seasonal models of SFV indicated that a cubic equation had the best fit. It was more practical to simulate seasonal water consumption models of trees with ESR. In further investigations, these models should be optimized.