Monsoon North Research Articles

Streamflow diurnal fluctuation and driving mechanism of headwater stream in a semi-humid mountainous region

Diurnal fluctuation in streamflow during rainless periods provides valuable signals for the calibration of hydrological models and comprehension of hydrological processes. Previous research has primarily focused on this phenomenon in the context of single-factor analysis in the Mediterranean, Maritime, and Alpine climates of Middle Europe and Western US. This study is based on the Xitaizi Experimental Watershed (XEW), a typical mountainous headwater watershed situated in the semi-humid monsoon North China Plain. Seven years of high-frequency observation data were used to investigate the characteristics of streamflow diurnal fluctuation, its driving mechanisms, and the propagation pathways of these fluctuation signals through hillslope-riparian-stream. The results are as follows: (1) Streamflow exhibits diurnal fluctuation during rainless periods throughout the year, with variations up to 36% of the daily mean and distinct patterns in rainy (peak at night) and dry seasons (peak in the afternoon). Choosing the proper timing for daily discharge observation can reduce bias due to fluctuations. (2) In rainy seasons, the impact of discharge fluctuation is significant, particularly in years with lower discharge. Meanwhile, the soil moisture in both the hillslope and the riparian zone, and the groundwater level in the riparian zone exhibit a daytime decline and a nighttime rise. The groundwater level in the hillslope fluctuates with a lag time of approximately 6 to 9 hours. (3) Numerical simulations and cross-correlation analysis demonstrate that the dominant driving mechanism of diurnal fluctuations in rainy seasons is the diurnal evapotranspiration variation in the riparian zone, while the influence of aquifer hydraulic conductivity is insignificant.

Late Neolithic community, clay pipes and water diversion in monsoonal North Central China

Late Neolithic community, clay pipes and water diversion in monsoonal North Central China

The difference between threshold of oil sludge discharge to the sea based on MARPOL 1973/1978 and the provision of oil sludge threshold in Indonesia’s seawater quality regulation that causes pollution in Bintan Coast, Indonesia

The coast of Bintan, Indonesia, has long been polluted by oil sludge. pollution caused by oil sludge in coastal areas continues and worsens during the north monsoon season, and has not been resolved to date. This occurs because there are differences in determining the threshold for disposing of oil waste into the sea based on MARPOL 1973/1978 and the provision of oil sludge threshold in Indonesia’s seawater quality regulation that causes pollution in Bintan Coast, Indonesia. Research into this provision must be carried out immediately in order to stop the pollution that occurs. The research carried out is prescriptive research, which aims to obtain advice regarding what should be done about the problem being studied. Legal materials collected through field research and book research will be researched qualitatively. The results of its application provide an understanding of the realization of the correct implementation of the normative legal rules being investigated. So it is necessary to amend the threshold for oil waste disposal regulated in MARPOL by adapting to the sea water quality standard regulations for each country, especially in this case there is a clear difference in the threshold compared to the provision of oil sludge threshold in Indonesia.

Selecting CMIP6 GCMs for CORDEX Dynamical Downscaling: Model Performance, Independence, and Climate Change Signals

AbstractGlobal climate models (GCMs) are essential for investigating climate change, but their coarse scale limits their efficacy for climate adaptation planning at the regional scales where climate impacts manifest. Dynamical downscaling of GCM outputs better resolves regional climate and thus provides improved guidance for climate policy at regional scales. Being expensive to run, downscaling uses a subset of GCMs, necessitating careful GCM selection. This evaluation identifies a suitable subset of CMIP6 GCMs for downscaling over Australia by assessing individual GCMs against three criteria: (a) performance simulating daily climate variable distributions, climate means, extremes, and modes; (b) model independence; and (c) climate change signal diversity. Over Australia, GCMs are generally biased cold (warm) for maximum (minimum) temperature, with larger biases for minimum temperature. GCMs are generally wet biased, especially over the monsoonal north, but dry biased over eastern regions. Most GCMs show larger biases for temperature and precipitation over geographically complex, heavily populated eastern regions, relative to other regions. Evaluations identify a distinct group of 11 GCMs that perform consistently poorly across climate variables, statistics, and timescales with widespread, statistically significant biases, versus 13 GCMs that show consistent adequate‐to‐good performance with substantially reduced errors. Assessment of model independence highlights the lack of independence between several high‐performing GCMs, particularly from allied modeling groups, demonstrating the importance of careful ensemble selection when making selective samples of climate space. Once GCM climate signal diversity is considered, 6–8 mid‐to‐high‐performing, independent GCMs occupy the full range of the future climate space and, thus, are suitable for dynamical downscaling over CORDEX‐Australasia.

Decadal changes of the early summer Asian monsoon and the South China Sea tropical cyclones during 2001\u20132020

An inter-decadal increase (1990–2009) in the western North Pacific (WNP) tropical cyclone (TC) genesis frequency in May has recently been reported. The TC decadal changes was attributed to an advanced monsoon onset over the Asian Summer Monsoon region, particularly over the South China Sea (SCS) in May. In the present study, we used 60 years (1961–2020) of TC data and 40 years (1981–2020) of the global reanalysis data to investigate the unique changes of the SCS TC activity during May and the associated large-scale environment. We find that the increasing trend was weakened during the most recent decade (2011–2020), and the advanced monsoon onset was not discernable. The period of 2011–2020 was identified as a decade of the minimum TC genesis frequency over the SCS in May since 1961. The extremely inactive TC genesis was attributed to the weak low-level cross equatorial monsoonal flow over the Indo-Pacific warm pool and the weak westerly monsoon (easterly anomalies) north of equator from the western Pacific through the Philippine Sea and the SCS to the Bay of Bengal. The weak tropical monsoon was associated with subtropical anticyclonic and suppressed convection north of the equator and the opposite wind and convection south of the equator. The anticyclonic circulation over the SCS was particularly strong that inhibited TC genesis during the first decade of the twenty-first century.

Unrecognized Ant Megadiversity in Monsoonal Australia: Diversity and Its Distribution in the Hyperdiverse Monomorium nigrius Forel Group

We document diversity and its distribution within the hyperdiverse Monomorium nigrius Forel group of the Australian monsoonal tropics, an unrecognized global centre of ant diversity. The group includes a single described species, but several distinct morphotypes each with multiple clearly recognizable taxa are known. Our analysis is based on 401 CO1-sequenced specimens collected from throughout the Australian mainland but primarily in the monsoonal north and particularly from four bioregions: the Top End (northern third) of the Northern Territory (NT), the Sturt Plateau region of central NT, the Kimberley region of far northern Western Australia, and far North Queensland. Clade structure in the CO1 tree is highly congruent with the general morphotypes, although most morphotypes occur in multiple clades and are therefore shown as polyphyletic. We recognize 97 species among our sequenced specimens, and this is generally consistent (if not somewhat conservative) with PTP analyses of CO1 clustering. Species turnover is extremely high both within and among bioregions in monsoonal Australia, and the monsoonal fauna is highly distinct from that in southern Australia. We estimate that the M. nigrius group contains well over 200 species in monsoonal Australia, and 300 species overall. Our study provides further evidence that monsoonal Australia should be recognized as a global centre of ant diversity.

BrGDGTs-based temperature and hydrological reconstruction from fluvio-lacustrine sediments in the monsoonal North China Plain since 31 kyr BP

Knowledge of glacial-interglacial changes in the East Asian summer monsoon (EASM) can potentially provide insights into future hydrological changes in its region of influence, caused by ongoing global warming. Here, we present temperature and hydrological (soil moisture and pH) reconstructions based on records of branched glycerol dialkyl glycerol tetraethers from fluvio-lacustrine sediments in the monsoonal North China Plain (NCP) for the past 31 kyr. The results show that the air temperature in the NCP was ∼8–9 °C warmer during the mid-Holocene than during the Last Glacial Maximum, and that soil pH is negatively correlated with soil moisture but with a lag of 2–4 kyr due to the buffering effect of carbonates. By contrast, soil moisture increased synchronously with temperature, suggesting that EASM precipitation will increase in the near future as global warming continues. Additionally, the initial increase in land and sea temperature during the last deglaciation lagged summer insolation at northern high latitudes, indicating that insolation was the ultimate trigger of the last deglacial warming.

Wave Energy Potential for Development of Renewable Energy in Riau Archipelago Province

Energy and electricity demand in Riau Islands is increasing rapidly due to the fast-growing population, urbanization, industrial development, and economic growth. The limitations of energy and electricity in the Riau Islands caused frequent blackouts. To support the high demand for energy and electricity in the Riau Islands, renewable energy is the most suitable alternative energy solution. Renewable energy is not only playing a key role in providing energy but also providing long-term clean and sustainable energy. We investigated the wave energy potential in the Riau Islands Sea in four different consecutive monsoons (North monsoon, East monsoon, South Monsoon and West Monsoon) using ECMWF data during January 2018 to December 2018 with 0.125o x 0.125o and 6 hourly spatial and temporal resolutions. We extracted bathymetry data from NOAA’s database ETOPO1 and forecasting wave characteristics use the SPM (Shore Protection Manual) method. The potential wave energy simulation from significant wave height (Hs) and energy period (Te) was shown in spatial distribution based on different monsoon. Our studies found that the potential wave energy was higher in north monsoon with maximum spatial of wave power density 3.240 – 3.640 kW.m-1. The east monsoon tended to be lower potential wave energy with dominance of wave power density at 0 – 0.127 kW.m-1. Keywords: wave power density, potential wave energy, ECWFM, monsoon

A revision of the Australian cicada genus Punia Moulds, 2012 (Cicadidae: Cicadettinae: Cicadettini) with the description of four new species.

Punia minima (Goding Froggatt, 1904) from the Northern Territory is redescribed and the female described for the first time. Four new species found across the monsoonal north of Australia are documented: P. hyas sp.n., P. limpida sp.n., P. kolos sp.n. and P. queenslandica sp.n. A key to all five species is provided and their phylogenetic relationships discussed.

Hydroclimate extremes in a north Australian drought reconstruction asymmetrically linked with Central Pacific Sea surface temperatures

An understanding of tropical hydroclimate variability, the associated drivers and how it is likely to change is a major scientific and societal challenge that is acutely hampered by short instrumental records. We present a 246-year tree-ring drought reconstruction of the Standardised Precipitation Evaporation Index (SPEI) for monsoonal northern Australia for the end of the wet season (March–May; MAM). This reconstruction extends the instrumental record back by 150 years. Around one third of total annual rainfall falls during MAM, making it a crucial component of the monsoonal cycle. MAM is also the season most impacted by the differential decay process of Central Pacific (as opposed to Western Pacific) El Nino events that are linked with dry conditions over northern and northwestern Australia more generally. Our reconstruction therefore provides an opportunity to consider how central Pacific variability has modulated MAM hydroclimate in Australia's monsoonal north over the past two and a half centuries. We found that MAM hydroclimate extremes in the region have a strong, but asymmetric relationship with central Pacific sea surface temperatures (SSTs) and ENSO indices. Extremely wet MAMs in monsoonal north Australia were associated with cooler SSTs, above average rainfall across much of Australia, and often coincided with La Nina events. The spatial relationship between dry extremes and Pacific SSTs during dry events was generally, but weakly, consistent with the SST signature of central Pacific El Nino events. The association between reconstructed dry extremes in the monsoonal north and dry conditions across the rest of Australia is also less extensive and weaker than for wet events. Results suggest that more extreme wet events in the Australian monsoonal north likely reflect cool central Pacific SSTs and later termination of the Australian monsoon. Consecutive years with extremely dry MAMs became more frequent over the latter part of the 20th Century while the probability of an extreme dry MAM followed by an extreme wet MAM the next year peaked in the mid 20th Century and has since declined.

The impact of global warming and the El Ni\xf1o-Southern Oscillation on seasonal precipitation extremes in Australia

The El Niño-Southern Oscillation (ENSO) drives substantial variability in precipitation and drought risk over Australia. Understanding the combined effect of anthropogenic forcing and ENSO on Australian precipitation extremes over the coming century can assist adaptation efforts. Here we use 24 CMIP5 climate models to examine externally forced changes in the frequency of “droughts”, when precipitation falls below the pre-industrial Decile 1 threshold. We focus on June to November (i.e., southern hemisphere Winter–Spring season) because precipitation during this period is important for agricultural production and recharging reservoirs in many parts of the country. The analysis in this paper is based on two 90-year simulations (1900–1989 and 2010–2099) for Historical and RCP8.5 scenarios. We show that the frequency of droughts, including droughts occurring in consecutive Winter–Spring seasons, is projected to increase in the twenty-first century under the RCP8.5 scenario in all eight Natural Resource Management (NRM) “clusters”. Approximately 60% of years are projected to be drought years in Perth, 35% in Adelaide, 30% in Melbourne, and approximately 20–25% of years in Sydney, Canberra and Brisbane. The relative frequency distributions of seasonally averaged Winter–Spring precipitation shift to lower values in all NRM clusters. However, apart from the Southern and Southwestern Flatlands, the shifts are accompanied by changes in the shape of the distributions whereby the high end of the distributions do not shift as much as other parts of the distribution and the wettest seasons become marginally wetter. This means that in most locations generally drier conditions are projected to be infrequently punctuated by seasons that are just as wet or wetter than the wettest years experienced during the twentieth century. While the models generally do a poor job in simulating ENSO precipitation teleconnections over Australia, an increase in ENSO-driven variability is suggested for the Wet Tropics, the Monsoonal North, the Central Slopes and the Southern and Southwestern Flatlands.

The impact of perceived heat stress symptoms on work-related tasks and social factors: A cross-sectional survey of Australia's Monsoonal North

Heat poses a significant occupational hazard for labour-intensive workers in hot and humid environments. Therefore, this study measured the prevalence of heat-stress symptoms and impact of heat exposure on labour-intensive industries within the Monsoonal North region of Australia. A cohort of 179 workers completed a questionnaire evaluating environmental exposure, chronic (recurring) and/or severe (synonymous with heat stroke) symptoms of heat stress, and impact within work and home settings. Workers reported both chronic (79%) and severe (47%) heat stress symptoms, with increased likelihood of chronic symptoms when exposed to heat sources (OR 1.5–1.8, p = 0.002–0.023) and decreased likelihood of both chronic and severe symptoms when exposed to air-conditioning (Chronic: OR 0.5, p = <0.001, Severe: OR 0.7, p = 0.019). Negative impacts of heat exposure were reported for both work and home environments (30–60% respectively), highlighting the need for mitigation strategies to reduce occupational heat stress in the Monsoonal North.

Shallow Cross‐Equatorial Gyres of the Indian Ocean Driven by Seasonally Reversing Monsoon Winds

AbstractInterior, cross‐equatorial transports are unique phenomena of the Indian Ocean, fluxing heat and salt between hemispheres. We use real and simulated surface drifter trajectories to reveal three cross‐equatorial gyres in the northern Indian Ocean that are driven by the seasonally reversing monsoon winds. Simulated trajectories are computed by advecting hundreds of thousands of particles through a monthly drifter climatology. Gyres are depicted using probabilistic pathlines, defined as the most common trajectories that cross the equator within the Somali Current. Northward pathlines in boreal spring and summer split into two gyres: A 1‐year loop contained west of the Maldives, described as a wind‐driven overshoot of the Southern Hemisphere equatorial gyre, and a 2‐year figure‐of‐eight, encompassing the Great Whirl and reaching the eastern boundary via the equatorial Wytrki jet, to return westward within the North Monsoon Current. Both these gyres include cross‐equatorial flow, driven by southward Ekman drift during the southwest monsoon. Southward pathlines through the Somali Current in winter originate in the dissipating Great Whirl and feed eastward into the South Equatorial Counter Current. Eighty‐five percent of simulated trajectories participate in these gyres, with significant leakage into the Bay of Bengal (14%) and Mozambique Channel (8%). A striking result of our analysis is the lack of pathlines connecting the Somali Current and coastal upwelling regions with the Arabian Basin, in contrast to the continuous coastal current that seasonal streamlines depict. Geostrophic pathlines reveal slow connectivity between these regions below the surface. Consideration of upwelling and subduction is reserved for subsequent modeling studies.

A 507-year rainfall and runoff reconstruction for the Monsoonal North West, Australia derived from remote paleoclimate archives

The Monsoonal North West (MNW) region of Australia faces a number of challenges adapting to anthropogenic climate change. These have the potential to impact on a range of industries, including agricultural, pastoral, mining and tourism. However future changes to rainfall regimes remain uncertain due to the inability of Global Climate Models to adequately capture the tropical weather/climate processes that are known to be important for this region. Compounding this is the brevity of the instrumental rainfall record for the MNW, which is unlikely to represent the full range of climatic variability. One avenue for addressing this issue (the focus of this paper) is to identify sources of paleoclimate information that can be used to reconstruct a plausible pre-instrumental rainfall history for the MNW. Adopting this approach we find that, even in the absence of local sources of paleoclimate data at a suitable temporal resolution, remote paleoclimate records can resolve 25% of the annual variability observed in the instrumental rainfall record. Importantly, the 507-year rainfall reconstruction developed using the remote proxies displays longer and more intense wet and dry periods than observed during the most recent ~100years. For example, the maximum number of consecutive years of below (above) average rainfall is 90% (40%) higher in the rainfall reconstruction than during the instrumental period. Further, implications for flood and drought risk are studied via a simple GR1A rainfall runoff model, which again highlights the likelihood of extremes greater than that observed in the limited instrumental record, consistent with previous paleoclimate studies elsewhere in Australia. Importantly, this research can assist in informing climate related risks to infrastructure, agriculture and mining, and the method can readily be applied to other regions in the MNW and beyond.

Tectonic uplift-influenced monsoonal changes promoted hominin occupation of the Luonan Basin: Insights from a loess-paleosol sequence, eastern Qinling Mountains, central China

Quaternary soil deposits from northern and southern China are distinctly different, reflecting variability of the East Asian monsoon north and south of the Qinling Mountains. Coeval sediments from the transitional climatic zone of central China, which are little studied to date, have the potential to improve our understanding of Quaternary monsoon changes and associated influences on hominin occupation of this region. Here, we investigate in detail a well-preserved and continuous Quaternary loess-paleosol sequence (Shangbaichuan) from the Luonan Basin, using a variety of weathering indices including major and trace element ratios, clay mineralogy, and Fe-oxide mineralogy. The whole-rock samples display similar rare earth element patterns characterized by upper continental crustal ratios: (La/Yb)N ≈ 9.5 and Eu/Eu* ≈ 0.65. Elemental data such as (La/Yb)N, La/Th and Eu/Eu* ratios show a high degree of homogeneity, suggesting that dust in the source region may have been thoroughly mixed and recycled, resulting in all samples having a uniform initial composition. Indices for pedogenic weathering such as Na/K, Ba/Sr, Rb/Sr, CIA, CIW, CPA, PIA, kaolinite/illite, (kaolinite + smectite)/illite, and hematite/(hematite + goethite) exhibit similar secular trends and reveal a four-stage accumulation history. The indices also indicate that the climate was warmer and wetter during the most recent interglacial stage, compared with coeval environments of the Chinese Loess Plateau. Secular changes in weathering intensity can be related to stepwise uplift of the Qinling Mountains and variation in East Asian monsoon intensity, both of which played significant roles in controlling climate evolution in the Luonan Basin. Furthermore, intensified aridity and winter monsoon strength in dust source areas, as evidenced by mineralogic and geochemical changes, may have been due to the mid-Pleistocene climate transition. Based on temporal correlation of warmer and wetter climatic conditions with more frequent hominin occupation, we infer that the paleoclimate in the eastern Qinling Mountains remained mild and favorable during glacial stages of the Late Quaternary, thus promoting early human settlement.

Interannual variability of PDSI from tree-ring widths for the past 278 years in Baotou, China

This paper provides the first interannual variability of PDSI series in Central Inner Mongolia, China. A Pinus tabulaeformis tree-ring-width chronology in Baotou, China, was developed. Based on the chronology, we reconstructed the local interannual variability of the Palmer Drought Severity Index (PDSI) from the previous September to current July (PDSIp9–7) for the past 278 years. The reconstruction explained 41.3% of the variance (40.3% after adjusting the degrees of freedom) of the actual interannual variability of the PDSI during the calibration period (1951–2012 AD). The spectral analyses revealed 3.5-, 2.6-, 2.3-, 2.1- and 2-year quasi-cycles at a 95% confidence level and 7.9-, 7.1- and 5.2-year quasi-cycles at a 90% confidence level. The PDSI reconstruction series was consistent with several reconstructed climatic series based on the tree-ring chronology in neighboring regions. The PDSIp9–7 exhibits excellent regional representativeness, which indicates the consistency of the drought variation of the central part of the monsoon margin area in north China, whereas PDSIp9–7 can represent the drought history of the central part of the north monsoon margin area. In addition, significant relationships were found between the PDSIp9–7 series and the Arctic Oscillation, North Atlantic Oscillation, El Nino-Southern Oscillation and Pacific Decadal Oscillation series, which indicates that the PDSI variation in the study area was influenced by a combination of these factors.

Climate change impacts on Yangtze River discharge at the Three Gorges Dam

Abstract. The Yangtze River basin is home to more than 400 million people and contributes to nearly half of China's food production. Therefore, planning for climate change impacts on water resource discharges is essential. We used a physically based distributed hydrological model, Shetran, to simulate discharge in the Yangtze River just below the Three Gorges Dam at Yichang (1 007 200 km2), obtaining an excellent match between simulated and measured daily discharge, with Nash–Sutcliffe efficiencies of 0.95 for the calibration period (1996–2000) and 0.92 for the validation period (2001–2005). We then used a simple monthly delta change approach for 78 climate model projections (35 different general circulation models – GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to examine the effect of climate change on river discharge for 2041–2070 for Representative Concentration Pathway 8.5. Projected changes to the basin's annual precipitation varied between −3.6 and +14.8 % but increases in temperature and consequently evapotranspiration (calculated using the Thornthwaite equation) were projected by all CMIP5 models, resulting in projected changes in the basin's annual discharge from −29.8 to +16.0 %. These large differences were mainly due to the predicted expansion of the summer monsoon north and west into the Yangtze Basin in some CMIP5 models, e.g. CanESM2, but not in others, e.g. CSIRO-Mk3-6-0. This was despite both models being able to simulate current climate well. Until projections of the strength and location of the monsoon under a future climate improve, large uncertainties in the direction and magnitude of future change in discharge for the Yangtze will remain.

Variability of upper‐ocean characteristics and tropical cyclones in the South West Indian Ocean

AbstractTrack and intensity are key aspects of tropical cyclone behavior. Intensity may be impacted by the upper‐ocean heat content relevant for TC intensification (known as Tdy) and barrier layer thickness (BLT). Here the variability of Tdy and BLT in the South West Indian Ocean and their relationships with tropical cyclones are investigated. It is shown that rapid cyclone intensification is influenced by large Tdy values, thick barrier layers and the presence of anticyclonic eddies. For TC generation in the South West Indian Ocean, the parameter Tdy was found to be important. Large BLT values overlay with large Tdy values during summer. Both fields are modulated by the westward propagation of Rossby waves, which are often associated with ENSO. For example, the 1997–1998 El Niño shows a strong signal in Tdy, SST, and BLT over the South West Indian Ocean. After this event, an increasing trend in Tdy occurred over most of the basin which may be associated with changes in atmospheric circulation. Increasing SST, Power Dissipation Index and frequency of Category 5 tropical cyclones also occurred from 1980 to 2010. To further examine the links between tropical cyclones, Tdy, and BLT, the ocean response to Category 5 Tropical Cyclone Bansi that developed near Madagascar during January 2015 was analyzed. Its unusual track was found to be linked with the strengthening of the monsoonal north westerlies while its rapid intensification from Category 2 to Category 4 was linked to a high‐Tdy region, associated with a warm core eddy and large BLT.

Winter climate changes over East Asian region under RCP scenarios using East Asian winter monsoon indices

The changes in the winter climatology and variability of the East Asian winter monsoon (EAWM) for the late 21st century (2070–2099) under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios are projected in terms of EAWM indices (EAWMIs). Firstly, the capability of the climate models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) in simulating the boreal winter climatology and the interannual variability of the EAWM for the late 20th century (1971–2000) is examined. Nine of twenty-three climate models are selected based on the pattern correlations with observation and a multi-model ensemble is applied to the nine model data. Three of twelve EAWMIs that show the most significant temporal correlations between the observation and CMIP5 surface air temperatures are utilized. The ensemble CMIP5 is capable of reproducing the overall features of the EAWM in spite of some biases in the region. The negative correlations between the EAWMIs and boreal winter temperature are well reproduced and 3–5 years of the major interannual variation observed in this region are also well simulated according to power spectral analyses of the simulated indices. The fields regressed onto the indices that resemble the composite strong winter monsoon pattern are simulated more or less weakly in CMIP5 compared to the observation. However, the regressed fields of sea level pressure, surface air temperature, 500-hPa geopotential height, and 300-hPa zonal wind are well established with pattern correlations above 0.83 between CMIP5 and observation data. The differences between RCPs and Historical indicate strong warming, which increases with latitude, ranging from 1 to 5 °C under RCP4.5 and from 3 to 7 °C under RCP8.5 in the East Asian region. The anomalous southerly winds generally become stronger, implying weaker EAWMs in both scenarios. These features are also identified with fields regressed onto the indices in RCPs. The future projections reveal that the interannual variability of the indices will be maintained with an intensity similar to that of the present. The correlation between monsoon indices and Arctic Oscillation increases over time. On the other hand, the correlation between monsoon indices and North Atlantic Oscillation decreases.

Evaluation of the remote-sensing-based DIFFUSE model for estimating photosynthesis of vegetation

Vegetation captures carbon from the atmosphere through photosynthesis, the rate of which varies across space, through time and is determined by both physical and biological factors. Methods for estimating photosynthesis (A) vary in their complexity and in which driving processes they capture. Whilst the effect of diffuse shortwave irradiance on A is well understood, few models have explicitly incorporated the diffuse effect into estimates of A. Here we present the DIFFUSE model, a simple, generic, diffuse-light-based method for estimating A at the monthly time scale. This model is based on the assumption that, at the monthly time scale, the majority of variability in A can be explained by the variability in total and diffuse irradiance and in the fraction of shortwave irradiance absorbed by foliage (f). Comparison of model estimates to eddy flux tower-derived monthly A showed that the majority (83%) of variability in observed A could be explained by the DIFFUSE model. The diffuse fraction contributed 5 to 10% of the model's accuracy across many of Australia's coastal regions, but contributed up to 50% in the monsoonal north. Various aspects of the DIFFUSE model were tested including its performance relative to an example of the more commonly used “stress-scalar” type of photosynthesis model. In all tests, the DIFFUSE model performed at least as well as more complex alternative models, and often outperformed them. The strengths of DIFFUSE are its physical basis, its simplicity and transparency, and its minimalist data requirements — all of which are expected to make it useful to a wide variety of contexts and applications.