Climate-Induced Yield Losses for Winter Wheat in Henan Province, North China and Their Relationship with Circulation Anomalies

Risk analysis using climate-induced yield losses (CIYL) extracted from long-term yield data have been recognized in China, but the research focusing on the time-series characteristics of risk and the circulation signals behind yield losses still remains incomplete. To address these challenges, a case study on winter wheat production in Henan province, north China was conducted by using annual series of yield in 17 cities during 1988–2017 and monthly series of 15 types of large-scale oceanic-atmospheric circulation indices (LOACI). A comprehensive risk assessment method was established by combining the intensity, frequency, and variability of CIYL and principal component analysis (PCA). The results showed that the westernmost Henan was identified as the area of higher-risk. PCA and Mann–Kendall trend tests indicated that the southern, northern, eastern, and western areas in Henan province were classified as having different annual CIYL variations in these four sub-regions; the decreasing trend of CIYL in northern area was the most notable. Since the 2000s, a significant decline in CIYL was found in each sub-region. It should be noted that the key LOACI, which includes Tropical Northern Atlantic Index (TNA), Western Hemisphere warm pool (WHWP), and Southern oscillation index (SOI), indicated significant CIYL anomalies in some months. Furthermore, the regional yield simulation results using linear regression for the independent variables of year and various LOACI were satisfactory, with the average relative error ranging from 3.48% to 6.87%.

Assessment of a snow storage gradient across a maritime mountain environment: a ground penetrating radar investigation

<p>The Southern Alps of New Zealand experience some of the highest precipitation rates globally, and dramatic west to east climatic gradients. Our current knowledge of this precipitation distribution is based on weather station data and river discharge measurements, but there is a clear data gap in the high elevation, central Southern Alps. Here, estimates of precipitation strongly diverge. This problem exists because of the difficulties of quantifying the depth and distribution of snow in a remote, high-altitude mountainous region. In order to improve our knowledge of snow distribution within this data-poor region, snow depths of (< 10m) were assessed parallel to the prevailing westerly wind direction at five locations across the mountain range, between the névé of Franz Josef Glacier, Waiho catchment, to the west and Jollie Valley, Pukaki catchment, in the east. The geophysical method of Ground Penetrating Radar (GPR) was used because of its ability to image the deep snow packs experienced in the study region. Comparison of measurement techniques over the (< 3km) surveyed transects showed that ground-based GPR gave the best sample size (41000 samples) and accuracy due to the high spatial resolution. Airborne GPR (8571 samples) overestimated snow depth by 8 % in low-gradient homogenous terrain, and 24% in steep heterogeneous terrain. The difference is ascribed to the larger view area of the GPR in the airborne survey. Direct probing of snow depth also performed poorly in comparison to ground-based GPR when generalising snow distribution over an area. Across-mountain precipitation peaked ~5 km west of the main divide, between 1700 and 2000 m a.s.l, providing the first empirical support to existing estimates of the location of peak precipitation. Results show decreasing precipitation from 12 ma-1 at Franz Josef Glacier, in the Waiho catchment, to 1.8 ma-1 at Jollie River valley, in the Lake Pukaki catchment, 25 km to the south-east. Internal reflection horizons in snow-pack radargrams allowed snowfall events to be tracked, and a relationship lowland and mountain precipitation to be established. Snowfall accumulation 'factors' were derived for different atmospheric circulation indices, and these will enable improved accuracy in modelling of snow accumulation processes. Further research is required to refine the relationship between synoptic-classed accumulation rates and inter-annual variations in climatic circulation. These refinements of measurement techniques and quantification of and snow distribution and depth allow for better estimation of river discharge and timing estimates for, hydroelectric power generation, and glacier mass balance.</p>

Assessment of a snow storage gradient across a maritime mountain environment: a ground penetrating radar investigation

<p>The Southern Alps of New Zealand experience some of the highest precipitation rates globally, and dramatic west to east climatic gradients. Our current knowledge of this precipitation distribution is based on weather station data and river discharge measurements, but there is a clear data gap in the high elevation, central Southern Alps. Here, estimates of precipitation strongly diverge. This problem exists because of the difficulties of quantifying the depth and distribution of snow in a remote, high-altitude mountainous region. In order to improve our knowledge of snow distribution within this data-poor region, snow depths of (< 10m) were assessed parallel to the prevailing westerly wind direction at five locations across the mountain range, between the névé of Franz Josef Glacier, Waiho catchment, to the west and Jollie Valley, Pukaki catchment, in the east. The geophysical method of Ground Penetrating Radar (GPR) was used because of its ability to image the deep snow packs experienced in the study region. Comparison of measurement techniques over the (< 3km) surveyed transects showed that ground-based GPR gave the best sample size (41000 samples) and accuracy due to the high spatial resolution. Airborne GPR (8571 samples) overestimated snow depth by 8 % in low-gradient homogenous terrain, and 24% in steep heterogeneous terrain. The difference is ascribed to the larger view area of the GPR in the airborne survey. Direct probing of snow depth also performed poorly in comparison to ground-based GPR when generalising snow distribution over an area. Across-mountain precipitation peaked ~5 km west of the main divide, between 1700 and 2000 m a.s.l, providing the first empirical support to existing estimates of the location of peak precipitation. Results show decreasing precipitation from 12 ma-1 at Franz Josef Glacier, in the Waiho catchment, to 1.8 ma-1 at Jollie River valley, in the Lake Pukaki catchment, 25 km to the south-east. Internal reflection horizons in snow-pack radargrams allowed snowfall events to be tracked, and a relationship lowland and mountain precipitation to be established. Snowfall accumulation 'factors' were derived for different atmospheric circulation indices, and these will enable improved accuracy in modelling of snow accumulation processes. Further research is required to refine the relationship between synoptic-classed accumulation rates and inter-annual variations in climatic circulation. These refinements of measurement techniques and quantification of and snow distribution and depth allow for better estimation of river discharge and timing estimates for, hydroelectric power generation, and glacier mass balance.</p>

The Hydrological System and Climate of Brewster Glacier, Tititea Mt Aspiring National Park, Southern Alps, Aotearoa New Zealand, in the Context of Climate Change.

<p>Temporal and spatial variability of stream discharge is directly related to variation in local climate, and this in turn is related to both regional and global atmospheric circulation and climate change. The relationship is complicated in glacierised catchments. This study aims to identify relationships between discharge from Brewster Glacier proglacial stream and both local atmospheric variables and national atmospheric circulation patterns. An attempt is made to quantify these relationships using statistical models and tests in order that prediction of discharge with climate change could be made using local weather forecasts and national circulation indices. The nature of the subglacial drainage system is also investigated with particular focus on its structural evolution from summer to autumn. It is found that shortwave radiation, wind speed and relative humidity are consistently the most important variables in prediction of discharge and that wind speed is most important during summer while air temperature is most important in autumn. It is concluded that the importance of precipitation is greater than indicated by the results which were influenced by covariance in the records. A multiple regression model for summer discharge predicts up to 85% of variation in the proglacial stream hydrograph and for autumn 60%. Low overall energy inputs during autumn result in lesser sensitivity of discharge to variation in environmental conditions. It is concluded that the subglacial drainage system is highly arborescent over both summer and autumn and that little, if any, evolution occurs through these seasons. A qualitative relationship is established between discharge production at Brewster Glacier proglacial stream and national atmospheric circulation indices; highest average discharge occurs during northwesterly cyclonic conditions, when the turbulent heat fluxes and precipitation dominate discharge production, and lowest during southeasterly anticyclones when total energy inputs are low. The multiple regression models are used to estimate changes in discharge over the next 20 years given predicted changes in air temperature and precipitation, and it is found that the models lack the sensitivity required for accurate predictions.</p>

The Hydrological System and Climate of Brewster Glacier, Tititea Mt Aspiring National Park, Southern Alps, Aotearoa New Zealand, in the Context of Climate Change.

<p>Temporal and spatial variability of stream discharge is directly related to variation in local climate, and this in turn is related to both regional and global atmospheric circulation and climate change. The relationship is complicated in glacierised catchments. This study aims to identify relationships between discharge from Brewster Glacier proglacial stream and both local atmospheric variables and national atmospheric circulation patterns. An attempt is made to quantify these relationships using statistical models and tests in order that prediction of discharge with climate change could be made using local weather forecasts and national circulation indices. The nature of the subglacial drainage system is also investigated with particular focus on its structural evolution from summer to autumn. It is found that shortwave radiation, wind speed and relative humidity are consistently the most important variables in prediction of discharge and that wind speed is most important during summer while air temperature is most important in autumn. It is concluded that the importance of precipitation is greater than indicated by the results which were influenced by covariance in the records. A multiple regression model for summer discharge predicts up to 85% of variation in the proglacial stream hydrograph and for autumn 60%. Low overall energy inputs during autumn result in lesser sensitivity of discharge to variation in environmental conditions. It is concluded that the subglacial drainage system is highly arborescent over both summer and autumn and that little, if any, evolution occurs through these seasons. A qualitative relationship is established between discharge production at Brewster Glacier proglacial stream and national atmospheric circulation indices; highest average discharge occurs during northwesterly cyclonic conditions, when the turbulent heat fluxes and precipitation dominate discharge production, and lowest during southeasterly anticyclones when total energy inputs are low. The multiple regression models are used to estimate changes in discharge over the next 20 years given predicted changes in air temperature and precipitation, and it is found that the models lack the sensitivity required for accurate predictions.</p>

The influence of atmospheric circulation on the occurrence of dry and wet periods in Central Poland in 1954–2018

This work presents the influence of atmospheric circulation on the occurrence of dry and wet periods in the central Polish region of Kujawy. The material on which the authors relied encompassed monthly totals of precipitation obtained from 10 weather stations in the period 1954–2018. Both dry and wet periods have been identified on the basis of monthly values of the Standardised Precipitation Index (SPI). Additionally, the calendar of circulation types over Central Poland was used to determine the atmospheric circulation indices: western (W), southern (S) and cyclonicity (C). The analyses have indicated that the region concerned experiences low precipitation totals in comparison with the rest of Poland. According to the circulation indices W, S and C, for Central Poland, the air mass advection from the West prevails over that from the East. Moreover, a slightly more frequent inflow of air from the South than from the North has been observed. The frequency of anticyclonic situations is higher than that of the cyclonic types in this part of Europe. Drought spells occurred in the study area at a clear dominance of anticyclonic circulation, with the inflow of air mostly from the North and with increased westerly circulation. On the other hand, the occurrence of wet periods was mainly influenced by cyclonic circulation during the advection of the masses from the South and West. Dry and wet periods accounted for 28% and 27% of the study period, respectively.

Rice Yield Responses in Bangladesh to Large-scale Atmospheric Oscillation Using Multifactorial Model

This paper intends to explore rice yield fluctuations to large-scale atmospheric circulation indices (LACIs) in Bangladesh. The annual dataset of climate-derived yield index (CDYI), estimated using principal component analysis of Aus rice yield data of 23 districts, and five LACIs for the period 1980-2017 were used for this purpose. The key outcomes of the study were as follows: (1) three sub-regions of Bangladesh, northern, northwestern, and northeastern, showed different kinds of CDYI anomalies; (2) the CDYI time series in northern and northeastern regions exhibited a substantial 6-year fluctuation, whereas a 2.75 to 3-year fluctuation predominated the northwestern region; (3) rice yield showed the highest sensitivity of LACIs in the northern region; (4) Indian Ocean dipole (IOD) and East Central Tropical Pacific SST (Nino 3.4) in July, and IOD index in March provide the best yield forecasting signals for northern, northwestern, and northeastern regions, respectively; (5) wavelet coherence study demonstrated noteworthy in-phase and out-phases coherences between key climatic variables (KCVs) and CDYI anomalies at various time-frequencies in three sub-regions; (6) the random forest (RF) model revealed the IOD as the vital contributing factor of rice yield fluctuations in the country; (6) the multi-factorial model with different LACIs and year as predictors can predict rice yield, with the mean relative error (MRE) in the range of 4.82 to 5.51% only. The generated knowledge can be used for an early assessment of rice yield and recommend policy directives to ensure food security.

Observed and CMIP-simulated links between North Atlantic climatological winter jet latitude and inter-annual to decadal ocean-atmosphere coupling

&lt;p&gt;Decadal variability in indices of North Atlantic (NA) atmospheric circulation plays a major role in changing climate over western Europe. However, reproducing characteristics of this variability in climate models presents a major challenge. Climate models broadly exhibit weaker-than-observed multi-decadal variability in atmospheric circulation indices. A prominent explanation for this is that model-simulated links between anomalous sea-surface temperatures (SSTs) and atmospheric variability are too weak. The dominant mode of basin-wide NA SST variability is Atlantic multi-decadal variability (AMV), which on multi-decadal timescales is expressed more strongly over the NA sub-polar gyre (SPG). SSTs over the SPG region (SST&lt;sub&gt;SPG&lt;/sub&gt;) are therefore the main focus here.&lt;/p&gt;&lt;p&gt;Studies to date have shown that variability in the North Atlantic Oscillation (NAO) exhibits strongest correlations with AMV indices in late winter, but the reasons for this are not clear. Here we show that this stronger late-winter correlation is particularly clear for SST&lt;sub&gt;SPG&lt;/sub&gt; and coincides with a climatological equatorward shift of the eddy-driven NA westerly jet from early-to-late winter. To help gain dynamical insight, indices of eddy-driven jet latitude (JLI) and speed (JSI) were correlated with SST&lt;sub&gt;SPG&lt;/sub&gt; and it was found that they exhibit more pronounced early-to-late winter shifts in correlations than for the NAO; In particular, &amp;#160;correlations strengthen from early-to-late winter for JLI while weaken for JSI. Our results suggest that the jet-SST&lt;sub&gt;SPG&lt;/sub&gt; linkages progress through winter from JSI dominant in early winter to JLI dominant in late winter.&lt;/p&gt;&lt;p&gt;CMIP5 and CMIP6 models were then evaluated for representation of these observed characteristics in ocean-atmosphere linkages. Consistent with the observed sub-seasonal links between climatological jet latitude and atmosphere-ocean correlation strength, CMIP models with larger equatorward jet biases exhibit weaker JSI-SST&lt;sub&gt;SPG&lt;/sub&gt; correlations and stronger JLI-SST&lt;sub&gt;SPG&lt;/sub&gt; correlations. A pronounced early-winter equatorward bias in jet latitude in CMIP models could partially explain the weaker-than observed linkage between SSTs and atmospheric variability. &amp;#160;&lt;/p&gt;

Variability in Sea Ice Melt Onset in the Arctic Northeast Passage: Seesaw of the Laptev Sea vs. the East Siberian Sea

&lt;p&gt;The ice/snow melt onset (MO) is a critical triggering signal for ice-albedo positive feedback in the Arctic. Concerning the Northeast Passage (NEP), for 1979-1998, the MO in the East Siberian Sea (ESS) occurred generally earlier than that in the Laptev Sea (LS). However, for 1999-2018, the LS experienced significantly earlier MO than did the ESS in several years. This phenomenon is identified as the MO Seesaw (MOS), i.e., the MO difference between the LS and ESS. For the positive MOS, storm tracks in May tend to cover the ESS rather than the LS and easterly wind prevails and shifts slightly to a northerly wind in the ESS, resulting in higher surface air temperature (SAT) and total-column water vapor (TWV) and earlier MO in the ESS. For the negative MOS, storm tracks are much stronger in the LS than in the ESS and prominent southerly/southwesterly wind brings warm air from coastal land towards the LS. The effect of the Barents Oscillation (BO) on the MOS could be dated back to April. When the Barents Sea is centered with a low SLP in April, sea ice in the LS would be driven away from the coasts, leading to a lower sea ice area (SIA), which increases the surface latent heat flux and humidifies the overlying atmosphere. Along with an enhanced downward sensible heat flux, earlier regional average MO occurs in the LS. For 1999-2018, the MOS was more closely related to both the local variables and the large-scale atmospheric circulation indices.&lt;/p&gt;

INFLUENCE OF LARGE-SCALE ATMOSPHERIC PROCESSES ON SEASONAL RUNOFF OF LARGE SIBERIAN RIVERS

Based on daily runoff volumes of four large Siberian rivers (the Ob, Yenisei, Lena, and Kolyma) for 1936-2018, the regime and changes in the total annual and seasonal runoff are analyzed. High synchronous and asynchronous correlations between monthly river runoff and atmospheric circulation indices of hemispheric and regional scales are revealed. In recent decades, the total annual runoff and its variations have increased (the rate of increase is most pronounced for the Kolyma River). A change in water content within a year is heterogeneous: weak positive trends are characteristic of the spring flood runoff and the summer-autumn period, and a significant increase occurred in the winter months. High correlations with a 1-8-month shift made it possible to identify the most informative regions, the atmospheric circulation over which makes a certain contribution to the variance of river runoff.