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Various aspects of tropical cyclones (TCs) fluctuate with the diurnal cycle. TC size is critical to the extent of its damage, but diurnal variations in the growth of the outer region size have largely remained unexplored. This paper examines the diurnal variations in the growth of the radius of gale‐force winds (34 kt; R34) by analyzing best‐track data from 2001 to 2019 for both North Atlantic TCs and global TCs outside of the North Atlantic region. Statistically significant diurnal variations was found for R34 growth, with the maximum 6‐h growth rate occurring at 2100–0300 local solar time (LST) for North Atlantic TCs, and at 0300–0900 LST for global TCs excluding the North Atlantic which experienced rapid intensification (≥30 knots within 24 h). The higher R34 6‐h growth rates during the night were linked to a larger extent of very deep convective clouds with infrared brightness temperatures <208 K during this time. [ABSTRACT FROM AUTHOR]

This paper investigates the relationship between the growth of the 34‐kt wind radius (R34) of tropical cyclones (TCs) and their fullness using best‐track data from 2001 to 2020. The storms were categorized into four groups based on a fullness scale: FS1 (fullness ≤ 0.4), FS2 (0.4 < fullness ≤ 0.6), FS3 (0.6 < fullness ≤ 0.8), and FS4 (fullness > 0.8). These groups exhibit unique spatial patterns of very deep convective clouds with infrared brightness temperatures <208 K. The mean R34 growth rates in 24 hr decrease from FS1 to FS4, which is linked to the higher coverage of very deep convection around R34 in storms with lower fullness. This study demonstrates that TC fullness can characterize the spatial distribution of deep convection in storms and serve as a representation of the growth of TC outer region size. These results have implications for understanding the mechanisms behind TC outer size growth. Plain Language Summary: The destructive potential of tropical cyclones (TCs) is primarily determined by two key factors: intensity and the size of the outer region. While the impact of TC wind structure on TC intensification rates has been extensively studied, little has been done to explore its effect on the growth of the outer region. This study finds that storms with lower fullness had larger growth rates in the radius of gale‐force winds (34 kt or 17 m/s; R34). TC fullness is defined as the ratio of the extent of the outer‐core wind skirt to the outer‐core size of the TC. This is associated with the higher coverage of very deep convective clouds with infrared brightness temperatures below 208 K around R34 in storms with lower fullness. These findings shed light on the importance of wind structure in the growth of the outer region in TCs, which helps improve our understanding of how these storms change in outer‐core size. Key Points: Tropical cyclone fullness can serve as a reliable indicator of the distribution of very deep convectionStorms with lower fullness have a higher mean R34 growth rate over a 24‐hr periodMore intense convection occurred around R34 in storms with lower fullness, which promotes the growth of R34 [ABSTRACT FROM AUTHOR]

The transformation of an iminyl radical into a primary amine is a challenging task. A practical and green catalytic system to trigger difluoromethyl radicals is highly desired. Herein, we developed a metal-free photocatalytic radical annulation of 2-cyanoaryl acrylamides with [CF2HPPh3]+Br− to provide 4-amino-quinolinones in moderate to good yields. This protocol utilized an easily obtained and cheap organophotocatalyst and green solvent acetone/H2O, and had the advantages of simple operation and broad substrate scope. [ABSTRACT FROM AUTHOR]

Infrared brightness temperature and tropical cyclone (TC) data from 2000 to 2018 were used to investigate the relationships between the radius of maximum wind (RMW), radius of gale‐force winds (34 kt or 17 m/s; R34), and intensity for intensifying and expanding North Atlantic TCs. Different relationships between intensity and R34 were found for different RMWs. Very deep convective clouds with infrared brightness temperatures ≤208 K are mainly observed on the outer edge of the RMW when it is stable. In such a case, the TC intensifies and R34 expands rapidly when very deep convective clouds occur in both the inner and outer regions, and thus a linear relationship between the intensity and R34 occurs when the RMW is stable. Plain Language Summary: Previous studies have shown that the inner‐core size, usually defined as radius of maximum wind (RMW), is considered to be correlated with subsequent intensity changes closely, while the outer region size, usually defined as radius of gale‐force winds (34 kt or 17 m/s, R34), is found to be weakly correlated with intensity and intensity change of tropical cyclones (TCs). The changes of azimuthal‐mean tangential wind speed in the inner and outer regions are considered to be independent of each other. This study reveals a significant linear relationship between intensity and R34 when RMW is steady in North Atlantic TCs from 2000 to 2018. The constant RMW roughly responds to the stability of the convective heating distribution. Consequently, with more convection heating, TCs intensify more rapidly and R34 expands faster. The results in this paper may provide a new perspective for understanding the relationship between TC intensity and size. Key Points: Tropical cyclone (TC) intensity and radius of gale‐force wind (R34) are linearly related when the radius of maximum wind (RMW) is stableLinear relationships between TC intensity and R34 are different for different initial RMWTCs intensify more rapidly and R34 expands faster with more very deep convective clouds with a stable RMW [ABSTRACT FROM AUTHOR]

Diurnal variations in contraction of the radius of maximum tangential wind (RMW) of tropical cyclones (TCs) were assessed using best‐track data for 2001–2018. For RMW contractions before TC intensification, the largest RMW contraction rate in 6 hr at 0300–0900 local solar time (LST) was associated with the maximum coverage of very deep convective clouds with infrared brightness temperatures <208 K at 0300–0600 LST, which were found mostly outside the mean RMW. The maximum RMW contraction rate and maximum intensification rate occurred simultaneously in 6 hr at 0300–0900 LST for rapidly intensifying storms associated with the greatest coverage of very deep convective cloud at 0300–0600 LST at storm center. This was not the case for nonrapidly intensifying storms. The time‐dependence of RMW contraction indicates the importance of radiative forcing on TC structure. Plain Language Summary: The diurnal cycle is a fundamental characteristic of the variability of the global climate system. Various aspects of tropical cyclones (TCs) also fluctuate with the diurnal cycle. Diurnal oscillations in contraction of the radius of maximum wind (RMW) were found for different periods of TCs. For RMW contractions before TC intensification, the largest RMW contraction rate in 6 hr at 0300–0900 local solar time (LST) was associated with the maximum coverage of very deep convective clouds with infrared brightness temperatures <208 K at 0300–0600 LST, which were found mostly outside the mean RMW. For rapidly intensifying storms, the maximum RMW contraction rate and maximum intensification rate occurred simultaneously at 0300–0900 LST associated with the greatest coverage of very deep convective clouds at 0300–0600 LST at the storm center. No marked diurnal oscillations in contraction of the RMW were found for non‐rapidly intensifying storms. The contracted RMW is an efficient configuration for TC spin‐up. The diurnal variations of RMW contraction indicate the importance of radiative forcing on TC structure. Key Points: The maximum radius of maximum wind (RMW) contraction rate at 03–09 local solar time (LST) are found before tropical cyclone intensificationThe maximum RMW contraction rate and maximum intensification rate occurred simultaneously at 03–09 LST for rapidly intensifying stormsThe maximum RMW contraction rate at 03–09 LST is associated with the largest coverage of the very deep convective clouds at 03–06 LST [ABSTRACT FROM AUTHOR]

A comparison was made between seasonal and diurnal variations in the Integrated Multi-Satellite Retrievals for Global Precipitation Measurement (IMERG) version 06B Final run and TRMM Multi-Satellite Precipitation Analysis (TMPA) 3B42 version 7 products from April 2014 to March 2019. As for earlier IMERG versions, systematic differences between IMERG version 06B precipitation and TMPA precipitation data were larger over the oceans than over land. Systematic annual mean differences between the IMERG and TMPA data over the oceans were smaller for IMERG version 06B than for earlier IMERG versions, possibly because of updated calibration processes. The mean differences between the IMERG version 06B and TMPA data for tropical oceans were relatively smtropical Pacific for all four seasons were not. The diurnal amplitudes of the IMERG were smaller than those of the TMPA over most continents, and the differences increased with mean diurnal amplitudes. The diurnal amplitudes of the IMERG were larger than those of the TMPA data over the oceans. The differences between the phases of the precipitation diurnal harmonics in the IMERG and TMPA datasets varied widely in all four seasons, but the mean phases were almost the same over both the oceans and the land. The sources of the differences in diurnal precipitation amplitudes in the Bay of Bengal and along the west coast of Central America, which showed large diurnal ranges and rather different diurnal amplitudes, were assessed. Differences in seasonal means caused differences in diurnal amplitudes in the Bay of Bengal, but for Central America, differences in diurnal amplitudes were associated with seasonal mean diurnal amplitudes. [ABSTRACT FROM AUTHOR]

In this paper, diurnal variations in tropical cyclone (TC) intensification and decay over the ocean are considered for the global TC basins from 1982–2017 using best track data. Statistically significant diurnal variations are found for global TCs, with a maximum intensification over the period 03–09 local solar time (LST). No diurnal signals are detected for TC decay. The highest frequency of occurrence and highest rate of intensification at 03–09 LST for global TCs are associated with the largest coverage of the very deep convective clouds with IR BT < 208 K at 03–06 LST. TC vortex spin‐up is favored at early morning through diurnal circulation linked to very deep convection. Key Points: Maximum intensification rate is found at 03–08 LST for global TCsNo diurnal signals are detected for TC decayThe highest TC intensification rate at 03–08 LST is associated with the largest coverage of the very deep convective clouds at 03–06 LST [ABSTRACT FROM AUTHOR]

Three satellite-derived precipitation datasets [the Tropical Rainfall Measuring Mission Multisatellite Precipitation Analysis (TMPA) dataset, the NOAA Climate Prediction Center morphing technique (CMORPH) dataset, and the newly available Integrated Multisatellite Retrievals for Global Precipitation Measurement (IMERG) dataset] are compared with data obtained from 55 rain gauges mounted on floating buoys in the tropics for the period 1 April 2014–30 April 2017. All three satellite datasets underestimate low rainfall and overestimate high rainfall in the tropical Pacific Ocean, but the TMPA dataset does this the most. In the high-rainfall (higher than 4 mm day−1) Atlantic region, all three satellite datasets overestimate low rainfall and underestimate high rainfall, but the IMERG dataset does this the most. For the Indian Ocean, all three rainfall satellite datasets overestimate rainfall at some gauges and underestimate it at others. Of these three satellite products, IMERG is the most accurate in estimating mean precipitation over the tropical Pacific and Indian Oceans, but it is less accurate over the tropical Atlantic Ocean for regions of high rainfall. The differences between the three satellite datasets vary by region and there is a need to consider uncertainties in the data before using them for research. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, satellite‐based precipitation, clouds with infrared (IR) brightness temperature (BT), and tropical cyclone (TC) data from 2000 to 2015 are used to explore the relationship between precipitation, convective cloud, and TC intensity change in the Western North Pacific Ocean. An IR BT of 208 K was chosen as a threshold for deep convection based on different diurnal cycles of IR BT. More precipitation and colder clouds with 208 K < IR BT < 240 K are found as storms intensify, while TC 24 h future intensity change is closely connected with very deep convective clouds with IR BT < 208 K. Intensifying TCs follow the occurrence of colder clouds with IR BT < 208 K with greater areal extents. As an indicator of very deep convective clouds, IR BT < 208 K is suggested to be a good predictor of TC intensity change. Based upon the 16 year analysis in the western North Pacific, TCs under the conditions that the mean temperature of very deep convective clouds is less than 201 K, and the coverage of this type of clouds is more than 27.4% within a radius of 300 km of the TC center, will more likely undergo rapid intensification after 24 h. [ABSTRACT FROM AUTHOR]

Diurnal variations of the areas and temperatures in tropical cyclone convective cloud systems in the western North Pacific were estimated using pixel-resolution infrared (IR) brightness temperature (BT) and best-track data for 2000-2013. The mean areal extent of very cold cloud cover (IR BTs < 208 K) reached a maximum in the early morning (0000-0300 local solar time (LST)), then decreased after sunrise. This was followed by increasing cloud cover between 208 and 240 K, reaching its maximum areal extent in the afternoon (1500-1800 LST). The time at which cloud cover reached a maximum was sensitive to the temperature thresholds used over the ocean. IR BTs < 240 K reached minima in the morning (0300-0600 LST), and IR BTs > 240 K reached minima in the afternoon (1500-1800 LST). The out-of-phase relationships between IR BTs < 240 K and IR BTs > 240 K, and between the maximum coverage times of IR BTs < 208 K and 208 K < IR BTs < 240 K, can both lead to the radius-averaged IR temperature having two minima per day. The different diurnal evolutions under different cloud conditions suggest tropical cyclone convective cloud systems are best described in terms of both areal extent and cloud-top temperature. Maximum occurrence of clouds with IR BTs < 208 K in the morning and maximum occurrence of clouds with 208 K < IR BTs < 240 K in the afternoon suggest that two different mechanisms might be involved in causing diurnal variations under these two types of tropical cyclone cloud conditions. [ABSTRACT FROM AUTHOR]

The sensitivity of the East Asian Monsoon (EAM) precipitation prediction skill to the variabilities of the tropical Indian and Pacific sea surface temperature (SST), the North Atlantic Oscillation (NAO), and the heating and snow cover over the Tibetan Plateau is evaluated in the framework of a linear Markov model. It is found that the tropical Indo-Pacific SST helps to improve the prediction of EAM precipitation over oceanic regions and some localized areas over land, while the Indian Ocean alone does not show significant impact on prediction. The remote effects of NAO improve the prediction in the middle and lower reaches of the Yangtze and Huaihe River valleys in boreal spring, fall and winter, and over oceanic areas in boreal summer and fall. The predictive skill of our model is not sensitive to the inclusion of the sensible heating and snow cover over the Tibetan Plateau, probably because their effects are implicitly present in the original EAM model. [ABSTRACT FROM AUTHOR]

Highlights: [•] Strong central Pacific El Niño and large diurnal variations were observed in 2009–2010. [•] Weakening of trade winds by westerly wind events lead to large diurnal variations. [•] Accumulated effect of diurnal cycle of SST may contribute to central Pacific El Niño warming. [ABSTRACT FROM AUTHOR]

A linear Markov model has been developed to predict the short-term climate variability of the East Asian monsoon system, with emphasis on precipitation variability. Precipitation, sea level pressure, zonal and meridional winds at 850 mb, along with sea surface temperature and soil moisture, were chosen to define the state of the East Asian monsoon system, and the multivariate empirical orthogonal functions of these variables were used to construct the statistical Markov model. The forecast skill of the model was evaluated in a cross-validated fashion and a series of sensitivity experiments were conducted to further validate the model. In both hindcast and forecast experiments, the model showed considerable skill in predicting the precipitation anomaly a few months in advance, especially in boreal winter and spring. The prediction in boreal summer was relatively poor, though the model performance was better in an ENSO decaying summer than in an ENSO developing summer. Also, the prediction skill was better over the ocean than the land. The model's forecast ability is attributed to the domination of the East Asian monsoon climate variability by a few distinctive modes in the coupled atmosphere-ocean-land system, to the strong influence of ENSO on these modes, and to the Markov model's capability to capture these modes. [ABSTRACT FROM AUTHOR]

Rainbands are essential to tropical cyclones (TCs), significantly affecting TC structure and intensity change. High‐resolution synthetic aperture radar (SAR) imagery can capture the footprints of rainbands caused by rain‐induced sea surface roughness modification. Using 464 SAR TC images, we investigated the rainband‐occurrence probability of TCs under different hemispheres, local times (LTs), intensities, and ocean basins. Results show that the rainband‐occurrence probability is highest in the downshear‐left quadrant for Northern Hemisphere TCs (downshear‐right quadrant for Southern Hemisphere TCs). For Northern Hemisphere TCs, the rainband‐occurrence probability is overall higher in the early morning (LT), and the peak region of rainband‐occurrence probability appears farther from the TC center in the evening (LT). Compared with weak TCs, the rainband‐occurrence probability becomes higher for strong TCs in the Northern Hemisphere. Furthermore, TCs have a higher rainband‐occurrence probability in the Northwest Pacific than in the North Atlantic and Northeast Pacific. Plain Language Summary: Rainbands are a salient feature of tropical cyclones (TCs) and are closely related to TC structure and intensity change. Synthetic aperture radar (SAR) can capture the sea surface imprint of rainbands beneath clouds caused by rain‐induced sea surface roughness modification. Using 464 SAR TC images, we made 464 rainband‐annotated data. The data were mapped to grid nodes spaced at 0.027 times the radius of max winds in a coordinate system with the origin at the TC center and the y‐axis in the vertical wind shear direction. Then, the data were composited to estimate and further investigate the rainband‐occurrence probability of TCs under different hemispheres, local times (LTs), intensities, and ocean basins. Results show that the rainband‐occurrence probability is highest in the downshear‐left quadrant for Northern Hemisphere TCs (downshear‐right quadrant for Southern Hemisphere TCs). For Northern Hemisphere TCs, the rainband‐occurrence probability is overall higher in the early morning (LT), and the peak region of rainband‐occurrence probability appears farther from the TC center in the evening (LT). Compared with weak TCs, the rainband‐occurrence probability becomes higher for strong TCs in the Northern Hemisphere. Furthermore, TCs have a higher rainband‐occurrence probability in the Northwestern Pacific than in the North Atlantic and Northeast Pacific. Key Points: The sea surface imprint of tropical cyclone (TC) rainbands in many synthetic aperture radar images reveals their occurrence probabilityThe rainband‐occurrence probability is overall higher in the early morning than in the evening. The feature is more obvious in strong TCsThe peak region of the probability appears farther from the TC center in the evening than in the early morning [ABSTRACT FROM AUTHOR]

Background: Hypertension is the most common chronic disease and the leading risk factor for disability and premature deaths worldwide. Approximately 10–20% of all patients with hypertension and 15–18% of the general population who are treated for hypertension have resistant hypertension (RH). Patients with RH have a higher risk of end-organ damage, such as carotid intima–media thickening, retinopathy, left ventricular hypertrophy and heart failure, myocardial infarction, stroke, impaired renal function, and death than those with controlled blood pressure. In the present study, we applied echocardiography to patients with RH to evaluate myocardial work (MW) and determine whether it is predictive for the occurrence of adverse events within 3 years. Methods: We included 283 outpatients and inpatients aged ≥ 18 years who met the clinical criteria for RH, without arrhythmia and severe aortic valve stenosis, between July 2018 and June 2019. The patients were followed up for 3 years from starting enrollment, and any adverse event that occurred during the period was used as the observation end point. Each enrolled patient underwent a complete transthoracic echocardiogram examination, blood pressure was measured and recorded, and MW was then analyzed. Results: Eighty-two (28.98%) patients with RH had adverse events, such as myocardial infarction (n = 29, 35.36%), heart failure (n = 4, 0.05%), renal insufficiency (n = 40, 48.78%), renal failure (n = 2, 0.02%), cerebral infarction (n = 5, 0.06%), and cerebral hemorrhage (n = 2, 0.02%), and no death events occurred. In patients with RH and adverse events, global longitudinal strain (GLS) (− 16% vs. − 18%), the global work index (2079 mmHg% vs. 2327 mmHg%), global constructive work (2321 mmHg% vs. 2610 mmHg%), and global work efficiency (93% vs. 94%) were lower than those in patients without adverse events. However, global wasted work (GWW) was higher in patients with RH and adverse events than in those without adverse events (161 mmHg% vs. 127 mmHg%). GLS and GWW were the most significant in predicting adverse events. Conclusions: MW, especially GLS and GWW, is a good method to predict 3-year adverse events in patients with RH. [ABSTRACT FROM AUTHOR]

By using observation and reanalysis datasets, this study identified an enhanced impact that El Niño–Southern Oscillation (ENSO)-independent spring Indian Ocean basin mode (IOBM) has on summer precipitation in Xinjiang. We concluded that the dynamic origins of the ENSO-independent IOBM can be explained by the extratropical and tropical pathways observed during 1994–2020. Specifically, a barotropic wave train originated from the North Atlantic and placed the Central Asian region below an anomalously low geopotential height center that persisted from Feb-Mar to May-Jul. In a response, the subtropical westerly jet stream moved southwestward relative to the climatology, which was favorable for anomalous southerly low-level winds to enhance precipitation in Xinjiang. Within the tropical pathway, the water vapor circulation patterns manifested an anomalous cyclone over the tropical Indian Ocean and an anomalous anticyclone over the southern Tibetan Plateau extending to the Arabian Sea, which is a classic baroclinic Matsuno–Gill response to the IOBM. The northward transport of moisture flux from the Arabian Sea, which is associated with the anomalous anticyclone, could bring abundant water vapor into Xinjiang, thus increasing precipitation. A physics-based empirical model was further developed to seasonally predict summer precipitation in Xinjiang. The independent prediction skill (2006–2020) from the empirical model indicated that 56% of the variability in summer precipitation in Xinjiang was predictable one season in advance. Our results highlight the important role that the ENSO-independent Indian Ocean SST play in impacting the climate over arid Northwest China. • The impact that the IOBM has on summer precipitation in Xinjiang was reexamined. • The enhanced influence was attributed to the ENSO-independent aspect of the IOBM. • The dynamic origins can be explained by the extratropical and tropical pathways. • Our P-E model can skillfully predict summer precipitation one season in advance. [ABSTRACT FROM AUTHOR]

Compared to the zonal-mean Hadley cell (HC), our knowledge of the characteristics, influence factors and associated climate anomalies of the regional HC remains quite limited. Here, we examine interannual variability of the northern poleward HC edge over western Pacific (WPHCE) during boreal winter. Results suggest that interannual variability of the WPHCE is impacted by the El Niño-Southern Oscillation (ENSO) Modoki, North Pacific Oscillation (NPO) and North Atlantic Oscillation (NAO). The WPHCE tends to shift poleward during negative phase of the ENSO Modoki, and positive phases of the NPO and NAO, which highlights not merely the tropical forcing but also the extratropical signals that modulate the WPHCE. ENSO modoki, NPO and NAO modulate the WPHCE via inducing atmospheric anomalies over the western North Pacific. We further investigate the climatic impacts of the WPHCE on East Asia. The poleward shift of the northern descending branch of the WPHC results in anomalous upward (downward) motions and upper-level divergence (convergence) anomalies over south-central China (northern East-Asia), leading to increased (decreased) rainfall there. Moreover, pronounced cold surface air temperature anomalies appear over south-central China when the sinking branch of the WPHC moves poleward. Based on the temperature diagnostic analysis, negative surface temperature tendency anomalies over central China are mostly attributable to the cold zonal temperature advection and ascent-induced adiabatic cooling, while the negative anomalies over South China are largely due to the cold meridional temperature advection. These findings could improve our knowledge of the WPHCE variability and enrich the knowledge of forcing factors for East Asian winter climate. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests that mesoscale eddies have a strong influence on the distribution and behavior of zooplankton and micronekton. However, the mechanisms driving their responses to mesoscale eddies are not yet fully understood, largely due to the low resolution of previous observations. Underwater gliders equipped with acoustic equipment and environmental sensors provide an ideal means to obtain observations with high temporal and spatial resolutions. In this study, two underwater gliders were used to record environmental parameters and acoustic intensities across an anticyclonic eddy in the oligotrophic western North Pacific subtropical gyre in September 2019. Based on the variations in the sea surface current and sea surface height anomaly (SSHA) along the underwater glider tracks, the study area was divided into three subregions: eddy core (SSHA >27 cm), eddy periphery (27 cm > SSHA >20 cm), and ambient water (SSHA <20 cm). More intense backscattering occurred in the upper 800 m of the eddy core with mean area backscattering coefficient values that were 35.8% higher than those of the eddy periphery and 19.8% higher than those of the ambient water. The convergence associated with the eddy could explain that the largest animal congregations occurred in the upper 100 m of the eddy core at night. Downwelling of warmer and oxygen-rich water in the eddy core induced animals to accumulate toward the deep of the eddy core, while migrating downwards during the day. Both these results and the lack of spatial heterogeneity of chlorophyll -a in and around the anticyclonic eddy indicated that horizontal and vertical distributions of zooplankton and micronekton in the anticyclonic eddy in the oligotrophic ocean were less related to spatial variations in the phytoplankton, but might be associated with the combined effect of the physical process in the anticyclonic eddy and the diel vertical migration behavior of animals. Our results suggest that anticyclonic eddies can dynamically modulate the spatial distribution of biomass, leading to the formation of mesopelagic biomass hotspots in the oligotrophic oceans and strongly affecting the ecology and behaviors of top predators that prey on small animals. • Spatial heterogeneity in biomass distribution was observed in an anticyclonic eddy. • Redistribution of biomass occurs within anticyclonic eddies. • Anticyclonic eddies in oligotrophic oceans support mesopelagic biomass hotspots. [ABSTRACT FROM AUTHOR]

Despite the tremendous progress in the theory, observation and prediction of El Niño over the past three decades, the classification of El Niño diversity and the genesis of such diversity are still debated. This uncertainty renders El Niño prediction a continuously challenging task, as manifested by the absence of the large warm event in 2014 that was expected by many. We propose a unified perspective on El Niño diversity as well as its causes, and support our view with a fuzzy clustering analysis and model experiments. Specifically, the interannual variability of sea surface temperatures in the tropical Pacific Ocean can generally be classified into three warm patterns and one cold pattern, which together constitute a canonical cycle of El Niño/La Niña and its different flavours. Although the genesis of the canonical cycle can be readily explained by classic theories, we suggest that the asymmetry, irregularity and extremes of El Niño result from westerly wind bursts, a type of state-dependent atmospheric perturbation in the equatorial Pacific. Westerly wind bursts strongly affect El Niño but not La Niña because of their unidirectional nature. We conclude that properly accounting for the interplay between the canonical cycle and westerly wind bursts may improve El Niño prediction. [ABSTRACT FROM AUTHOR]

Firmness changes in Nanguo pears under different freezing/thawing conditions have been characterized by hyperspectral imaging (HSI). Four different freezing/thawing conditions (the critical temperatures, numbers of cycles, holding time and cooling rates) were set in this experiment. Four different pretreatment methods were used: multivariate scattering correction (MSC), standard normal variate (SNV), Savitzky-Golay standard normal variate (S-G-SNV) and Savitzky-Golay multiplicative scattering correction (S-G-MSC). Combined with competitive adaptive reweighted sampling (CARS) to identify characteristic wavelengths, firmness prediction models of Nanguo pears under different freezing/thawing conditions were established by partial least squares (PLS) regression. The performance of the firmness model was analyzed quantitatively by the correlation coefficient (R), the root mean square error of calibration (RMSEC), the root mean square error of prediction (RMSEP) and the root mean square error of cross validation (RMSECV). The results showed that the MSC-PLS model has the highest accuracy at different cooling rates and holding times; the correlation coefficients of the calibration set (Rc) were 0.899 and 0.927, respectively, and the correlation coefficients of the validation set (Rp) were 0.911 and 0.948, respectively. The accuracy of the SNV-PLS model was the highest at different numbers of cycles, and the Rc and the Rp were 0.861 and 0.848, respectively. The RMSEC was 65.189, and the RMSEP was 65.404. The accuracy of the S-G-SNV-PLS model was the highest at different critical temperatures, with Rc and Rp values of 0.854 and 0.819, respectively, and RMSEC and RMSEP values of 74.567 and 79.158, respectively. [ABSTRACT FROM AUTHOR]