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It's summer
\"Readers learn all about what makes Summer special and are encouraged to draw connections between the text and their own lives.\"--Amazon.com.
Book
What happens in summer?
Learn the answers to many questions about the characteristics of the summer season.-- Source other than Library of Congress.
Book
Northern Hemisphere Summer Insolation and Ice Volume Driven Variations in Hydrological Environment in Southwest China
The interpretation of stalagmite δ18O in terms of reflecting Asian summer monsoon (ASM) precipitation is still elusive. Here, we present high‐resolution stalagmite trace element ratios (X/Ca, X = Mg, Sr, Ba) records from southwest China covering 116.09 to 4.07 ka BP. δ18O, δ13C, and X/Ca values exhibit clear precessional cycles, with δ18O values reflecting ASM circulation/intensity, while X/Ca ratios capture local precipitation or evapotranspiration variations. Our results show that Northern Hemisphere summer insolation (NHSI) is the main driver of ASM intensity and precipitation phase variation, but global ice volume modulates the response magnitude of summer precipitation to insolation. During the Last Glacial Maximum, high ice volumes caused significant monsoon precipitation to decrease. In contrast to modern observations of the tripolar distribution of precipitation in China, our record is consistent with paleo‐precipitation records in southern and northern China.
Plain Language Summary
While it is well known that global changes have led to variations in the intensity and spatial distribution of Asian monsoon precipitation, the mechanisms behind this are not well understood. Paleoclimate records are essential for revealing the drivers behind monsoon variation. However, speleothem records from the Asian monsoon region rarely provide direct information on the amount of rainfall. Here we report on multiple indicator data sets from a stalagmite in southwestern China. It could help explore the variation of monsoon precipitation over the last ∼100,000 years. We find that the increase/decrease of Northern Hemisphere summer insolation controls the increase/decrease of Asian summer monsoon rainfall. In addition, global ice volume moderates the magnitude of rainfall response to insolation, and precipitation decreases significantly during high ice volume periods. Based on the present paleo‐precipitation records evidence, the existence of the spatial pattern of increasing/decreasing rainfall in central China corresponding to decreasing/increasing rainfall in northern and southern China remains ambiguous on the orbital scales, although the feature has been captured by some of the model simulations.
Key Points
Stalagmite trace elements are indicators of regional hydrological environmental variations in Southwestern China
Northern Hemisphere summer insolation and global ice volume modulate the phase and amplitude variations of regional hydrological environment
The meridional tripolar spatial pattern of precipitation in monsoon region in China on the orbital scale remains ambiguous
Journal Article
Changes in Sahel summer rainfall in a global warming climate: contrasting the mid-Pliocene and future regional hydrological cycles
The evolution of Sahel summer rainfall in the context of global warming is a severe socio-economic concern because of its widespread influences on local agriculture, water resource management, food security, infrastructure planning, and ecosystems. Based on the mid-Pliocene simulations from the Pliocene Model Intercomparison Project Phase 2 and the historical simulations and shared socio-economic pathway 5–8.5 experiments from the Coupled Model Intercomparison Project phase 6, the present study contrasts the Sahel summer rainfall changes between the past mid-Pliocene and near future global warming climates. The results show that the Western African summer monsoon (WASM) circulation, closely linked with the Sahel summer rainfall change, tends to strengthen in both the past and future global warming climates, but the monsoonal circulation strengthening is much more intense in the past warm period than in the projected warm future. This causes that the multi-model ensemble (MME) mean increase ratio of Sahel summer rainfall in the past warming climate is about twice to three times larger than that in the future warming climate for the same increase of global mean surface temperature (the regional rainfall increase ratio in the MME mean: about 19.6% per one degree Celsius of global warming in the mid-Pliocene simulations versus about 7.7% per one degree Celsius of global warming in the SSP5-8.5 future projections). Such a striking discrepancy in the regional circulation and hydrological cycle changes is mainly attributed to a dramatically stronger warming over the Canadian Archipelago and Greenland during the mid-Pliocene warm period relative to the projected near future. The more significant northern high-latitude warming during the mid-Pliocene enhances the meridional temperature gradient between the extratropical and tropical regions, which could induce an excessive northward shift of the Intertropical Convergence Zone and a stronger WASM, and thus result in a more intense hydrological cycle around the Sahel region. Our results highlight that besides the global mean temperature increase, meridional warming patterns are also essential for the changes of WASM and regional hydrological cycle in a warmer world. Implications for projecting the regional monsoon and hydrological cycle changes at longer time scales than in the near future are discussed.
Journal Article
Lemonade sun : and other summer poems
A collection of poems celebrating summer sights and sounds.
Book
Impact of Developing ENSO on Tibetan Plateau Summer Rainfall
The year-to-year variations of Tibetan Plateau (TP) summer rainfall have tremendous climate impacts on the adjoining and even global climate, attracting extensive research attention in recent decades to understand the underlying mechanism. In this study, we investigate an open question of how El Niño–Southern Oscillation (ENSO) influences the TP precipitation. We show that the developing ENSO has significant impacts on the summer rainfall over the southwestern TP (SWTP), which is the second EOF mode of the interannual variability of summer rainfall over the TP. The moisture budget indicates that both the suppressed vertical motion and the deficit of moisture contribute to the reduction of SWTP rainfall during El Niño’s developing summer, with the former contribution 4 times larger than the latter. Moist static energy analyses indicate that the anomalous advection of climatological moist enthalpy by anomalous zonal wind is responsible for the anomalous descending motions over the SWTP. The El Niño–related southward displacements of the South Asian high and the upper-level cyclonic anomalies over the west of TP stimulated by the suppressed Indian summer monsoon precipitation are two key processes dominating the anomalous zonal moist enthalpy advection over SWTP. Mean while, the India–Burma monsoon trough is strengthened during El Niño developing summer, which prevents the advection of water vapor into the SWTP, and thus contributes to the deficit of summer SWTP rainfall. Our results help to understand the complicated ENSO-related air–sea interaction responsible for the variability of TP precipitation and have implications for seasonal prediction of the TP climate.
Journal Article
Effects of intraseasonal oscillation on South China Sea summer monsoon onset
Understanding of South China Sea (SCS) summer monsoon (SCSSM) onset response to tropical intraseasonal oscillation (ISO) is critical for extended-range prediction of SCSSM onset. In this study, we investigate the effect of ISO on SCSSM onset for the period of 1980–2013. The 34 onset cases are classified into three groups, early onsets around May 6th, normal onsets around May 21st and late onsets around June 8th, and the late onsets are even later than the Indian monsoon onsets. Before each onset, the SCS experiences a dry ISO phase to precondition the convective energy due to the easterly wind anomalies of the wet ISO phase over the tropical Indian Ocean for the group of early onsets, over the southern Bay of Bengal monsoon region for the group of normal onsets and over the southern Indian monsoon region for the group of late onsets. After each onset, the SCSSM is supported by the westerly wind anomalies of the dry ISO phase over these associated regions. Each early SCSSM onset is triggered by the northwestward propagating Rossby wave of the wet ISO in the western Pacific which comes from the Indian Ocean. For each normal (late) onset, the SCSSM is triggered by synoptic-scale low-level westerlies in conjunction with seasonal low-level westerlies when the wet ISO moves to the northern Bay of Bengal region (Indian monsoon region), since this convection to the north of 10°N cannot excite the easterly wind anomalies associated with Kelvin wave responses over the SCS to suppress the convection. The mechanisms explaining the mean state-controlled ISO-SCSSM onset relationship are also discussed.
Journal Article