Low-latitude Zone Research Articles

Features of the Structure of the Winter Morning High- and Mid-Latitude Ionosphere

The structure of the winter morning (0500–0900 LT) ionosphere in the Northern and Southern hemispheres is studied in detail. For this, CHAMP satellite data for quiet conditions during the period of high solar activity of 2000–2002 are used. Careful analysis is used to identify electron concentration troughs: the high-latitude ionospheric trough; subauroral, or main, ionospheric trough; and mid-latitude ring ionospheric trough. In order to identify and separate the high-latitude and main ionospheric troughs, the model of auroral diffuse precipitation of the Polar Geophysical Institute is used, which describes the boundaries of low-latitude zone I and high-latitude zone II of auroral diffuse precipitation. The longitudinal variations of the precipitation boundaries are corrected using the DMSP satellite data. The problem of separating the troughs becomes more complicated with the passage of local time, because the main ionospheric trough is more strongly displaced to the pole than the auroral oval; therefore, its area of existence begins to overlap the area of existence of the high-latitude trough. In order to identify and separate the main and ring troughs, all, even weak, geomagnetic disturbances for the observation period are analyzed in detail. The asymmetry of the Northern and Southern hemispheres is considered, and similar and different characteristics are identified. Therefore, a more complete and accurate pattern of the structure of the morning ionosphere is obtained.

Evaluation Of Nearly Zero Energy Residential Buildings Design Strategies In Three Climatic Zones In Jordan

Designing zero or near zero-energy residential buildings will considerably help in reducing the general energy consumption. Geographically, Jordan retains three different altitude zones with unique climatic conditions for each which imperatively entails deploying different approaches to attain near zero-energy houses. This study aims to investigate the best economic feasible design strategies that possibly lead to near zero-energy residential buildings. Based on the most common detached house design-layout and materials on each zone, three case study houses were designed. The research methodology was based on three levels of efficiency. By using Design Builder, each efficiency level was examined by three design strategies: passive, active, and renewable energy design strategies in order to improve the energy performance of the buildings. The results showed that implementing the three levels concurrently would result in achieving the nearly zero-energy houses with efficient cost and less than 10 years payback period. In the high-land altitude zone, the annual consumption of power was reduced from 79.1 kwh/m2 to -13.6 kwh/m2. For the medium altitude zone, the annual consumption dropped down from 78.8 kwh/m2 to -16.5 kwh/m2. Finally, the annual consumption of electricity in the low-latitude zone decreased from 75.7 kwh/m2 to -21.1 kwh/m2.

Comparison of physical and biological responses to tropical cyclones between the low and middle latitude zones of the western North Pacific

Upper ocean conditions vary considerably between latitudes, which results in different responses of the ocean to tropical cyclones (TCs). During the TC season, many TCs in the western North Pacific (WNP) extend northward from the low latitude zone (LLZ) to the middle latitude zone (MLZ). We studied the differences in the influence of TCs on the LLZ and MLZ by comparing the changes in the mixed-layer depth (MLD), sea surface temperature (SST), and chlorophyll-a (Chl-a) concentrations before and after 32 typical TCs that occurred from 2006 to 2019 in these two regions. Although the mean intensity and transit time of these TCs in the MLZ were lower than in the LLZ, the mean MLD deepening was greater, the SST cooling was more significant, and the surface Chl-a concentration increases were more pronounced in the MLZ after TCs. Differences in the responses of these two WNP regions to TCs were directly related to the differences in their upper ocean conditions. Compared to the LLZ, the MLZ had a shallower MLD, nutricline, and subsurface chlorophyll maxima depth, lower temperature, and higher nutrient concentrations in the subsurface layers. The upper ocean conditions in this region were relatively more susceptible to alteration after TCs, and the subsurface water, nutrients, and phytoplankton were more readily brought to the surface, largely contributing to the SST cooling and surface phytoplankton bloom. In particular, as the latitude increases, the degree of response of MLD, SST and surface Chl-a concentration after TCs may be more pronounced. These findings indicate that differences in responses to TCs in ocean areas at different latitudes were mainly due to differences in upper ocean physical and biochemical structure rather than to intensity and transit time of TCs.

Effects of the Time Sampling Interval on the Angular Combination Characteristics of Moon-Based Earth Observations

Observation angles are of great importance with respect to Earth observation platforms. The richness of angular combination, i.e., the combination of three observational angles (viewing zenith angle, solar zenith angle, and relative azimuth angle), is an important parameter to illustrate the angle sampling capability of an Earth observation platform. Here, the angular combination characteristics of a Moon-based platform were investigated and compared with existing artificial satellites. Furthermore, the effects of the time sampling interval on the angular combination characteristics were analyzed using a newly established angular combination number index (ACNI). Results show that a Moon-based platform can complement angular sampling observations from existing satellites. We found that the time sampling interval has different effects on the angular combination for different observed points. Accordingly, the Earth’s surface can be divided into two zones with respect to its sensitivity to the time sampling interval. When the time sampling interval increased from 10 min to 2 h, the maximum loss of the angular combination reached 50% for the observed points in the mid–low latitude zone.

CALIOP-Based Quantification of Central Asian Dust Transport

Central Asia is one of the most important sources of mineral saline dust worldwide. A comprehensive understanding of Central Asian dust transport is essential for evaluating its impacts on human health, ecological safety, weather and climate. This study first puts forward an observation-based climatology of Central Asian dust transport flux by using the 3-D dust detection of Cloud-Aerosol LiDAR with Orthogonal Polarization (CALIOP). The seasonal difference of transport flux and downstream contribution are evaluated and compared with those of the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). Central Asian dust can be transported not only southward in summer under the effect of the South Asian summer monsoon, but also eastward in other seasons under the control of the westerly jet. Additionally, the transport of Central Asian dust across the Pamir Plateau to the Tibetan Plateau is also non-negligible, especially during spring (with a transport flux rate of 150 kg m−1 day−1). The annual CALIOP-based downstream contribution of Central Asian dust to South Asian (164.01 Tg) is 2.1 times that to East Asia (78.36 Tg). This can be attributed to the blocking effect of the higher terrain between Central and East Asia. Additionally, the downstream contributions to South and East Asia from MERRA-2 are only 0.36 and 0.84 times that of CALIOP, respectively. This difference implies the overestimation of the wet and dry depositions of the model, especially in the low latitude zone. The quantification of the Central Asian dust transport allows a better understanding of the Central Asian dust cycle, and supports the calibration/validation of aerosol-related modules of regional and global climate models.

Analysis of Solar Hemispheric Chromosphere Properties using the Kodaikanal Observatory Ca–K Index

Abstract The Kodaikanal Observatory has provided long-term synoptic observations of chromospheric activities in the Ca ii K line (393.34 nm) since 1907. This article investigates temporal and periodic variations of the hemispheric Ca–K-index time series in the low-latitude zone (±40°), utilizing the recently digitized photographic plates of Ca–K images from the Kodaikanal Observatory for the period of 1907–1980. We find that the temporal evolution of the Ca–K index differs from one hemisphere to another, with the solar cycle peaking at different times in the opposite hemisphere, except for cycles 14, 15, and 21, when the phase difference between the two hemispheres was not significant. The monthly averaged data show a higher activity in the northern hemisphere during solar cycles 15, 16, 18, 19, and 20, and in the southern hemisphere during cycles 14, 17, and 21. We notice an exponentially decaying distribution for each hemisphere’s Ca–K index and the whole solar disk. We explored different midterm periodicities of the measured Ca–K index using the wavelet technique, including Rieger-type and quasi-biennial oscillations on different timescales present in the time series. We find a clear manifestation of the Waldmeier effect (stronger cycles rise faster than the weaker ones) in both the hemispheres separately and the whole disk in the data. Finally, we have found the presence of the Gnevyshev gap (time interval between two cycle maxmima) in both the hemispheric data during cycles 15 to 20. Possible interpretations of our findings are discussed with the help of existing theoretical models and observations.

African continental free trade area (AfCFTA): projected economic impact assessment under future warming in CMIP6

Launched on 1 January 2021, the African Continental Free Trade Area (AfCFTA) aims to bring together 1.3 billion people in a US$3.4 trillion economic bloc. The World Bank estimates that the AfCFTA could lift tens of millions of people out of poverty by 2035. Previous studies have shown that an increase in annual mean temperature can significantly affect economic growth. The AfCFTA economy will therefore be affected by future warming. However, without the AfCFTA, the impact of the increased annual average temperature on local economies could be severe, further depriving low-income African countries of economic recovery. To assess the damage to regional economic growth caused by future warming, trend analyses are conducted in the aggregated historical CFSR/NCEP and CMIP6 (GFDL-ESM4) climate projection data from 1979 to 2100 for different emission pathways over some major continental economic centres. The long-term impact of surface temperature increase on gross regional product (GRP) per capita growth rates are investigated by fitting CMIP6 daily and annual mean temperatures to a log-polynomial regression model. The results show that an increase in annual mean temperature will significantly affect the economic growth of low latitude and altitude regions compared to high latitude and altitude regions. Most emerging African economies and many member states of the African Union and AfCFTA are located in this low latitude zone. This makes the economies of the newly created AfCFTA very vulnerable to climate change. Several studies suggest that FTAs can help reduce the economic vulnerability of developing countries. The results presented here can contribute to better design and implementation of economic, trade and climate policies in the AfCFTA to mitigate the economic impacts of future warming.

Effect of the Solar Zenith Angles at Different Latitudes on Estimated Crop Vegetation Indices

Normalization of anisotropic solar reflectance is an essential factor that needs to be considered for field-based phenotyping applications to ensure reliability, consistency, and interpretability of time-series multispectral data acquired using an unmanned aerial vehicle (UAV). Different models have been developed to characterize the bidirectional reflectance distribution function. However, the substantial variation in crop breeding trials, in terms of vegetation structure configuration, creates challenges to such modeling approaches. This study evaluated the variation in standard vegetation indices and its relationship with ground-reference data (measured crop traits such as seed/grain yield) in multiple crop breeding trials as a function of solar zenith angles (SZA). UAV-based multispectral images were acquired and utilized to extract vegetation indices at SZA across two different latitudes. The pea and chickpea breeding materials were evaluated in a high latitude (46°36′39.92″ N) zone, whereas the rice lines were assessed in a low latitude (3°29′42.43″ N) zone. In general, several of the vegetation index data were affected by SZA (e.g., normalized difference vegetation index, green normalized difference vegetation index, normalized difference red-edge index, etc.) in both latitudes. Nevertheless, the simple ratio index (SR) showed less variability across SZA in both latitude zones amongst these indices. In addition, it was interesting to note that the correlation between vegetation indices and ground-reference data remained stable across SZA in both latitude zones. In summary, SR was found to have a minimum anisotropic reflectance effect in both zones, and the other vegetation indices can be utilized to evaluate relative differences in crop performances, although the absolute data would be affected by SZA.

Possibilities of the usage of the total electron content in a low-latitude zone

Last years, the small quantity of ionosondes at low latitudes could not give a sufficient picture of behavior of the ionosphere in these areas. Now, reception of experimental data, their analysis and detection of total electron content (TEC) variations at low latitudes are an actual problem. When moving from describing the state of the ionosphere using vertical sounding parameters to describing using TEC, it is important to identify similarities and differences in their behavior in order to assess the possibilities of using TEC. This paper carries out research on four ways of TEC usage in low-latitude zone: (1) research of climatological peculiarities of the TEC behavior, (2) validation of up-to-date TEC models, (3) foF2 calculation according to observational TEC, and (4) peculiarities of TEC behavior during geomagnetic disturbances. Results for station Hainan show the following. 1. In addition to previous investigation it is shown, that the empirical global and local models of TEC provide the values close to observational ones, however climatological features of TEC behavior described by various models may still differ from each other and from the experimental data showing in this case TEC maxima of diurnal variation in the afternoons, seasonal variations in March and October, some slight winter anomaly. 2. In contrast to previous investigation it is shown that the closest to the experimental values of TEC are provided by the IRI-Plas model, while this model overestimates values, and the model NeQuick underestimates values compared to the observational ones. 3. For the first time, the ionospheric equivalent slab thickness τ, which plays the role of the coefficient of proportionality between TEC and NmF2, was compared for the IRI, IRI-Plas, NeQuick models with the experimental median τ(med) and it was shown, that the usage of observational TEC data and τ(med) for calculation of critical frequencies foF2 allows improving correspondence with experimental data by 1.2–2 times compared to the models. 4. Comparison of foF2 and TEC behavior has a particular importance during disturbances. Using the example of 15 strong magnetic storms (Dst < −50 nT), it was shown that, despite its global nature, the details of the TEC response strongly depend on the region. So, the peculiarities of δTEC in comparison with the mid-latitude region are the predominance of the positive phase, and a smaller value of response. The synchronism of variations δTEC and δfoF2 was very high, although there are cases of mismatch. Using the median τ(med) allows determining foF2 during disturbances and filling data gaps.

Tropical Cloud Cluster Environments and Their Importance for Tropical Cyclone Formation

Abstract This study uses a nonhierarchical cluster analysis to identify the major environmental circulation patterns associated with tropical cloud cluster (TCC) formation in the western North Pacific. All TCCs that formed in July–October 1981–2009 are examined based on their 850-hPa wind field around TCC centers. Eight types of environmental circulation patterns are identified. Of these, four are related to monsoon systems (trough, confluence, north of trough, and south of trough), three are related to easterly systems (low-latitude zone, west of subtropical high, and southwest of subtropical high), and one is associated with low-latitude cross-equatorial flow. The genesis potential index (GPI) is analyzed to compare how favorable the environmental conditions are for tropical cyclone (TC) formation when TCCs form. Excluding three cluster types with the GPI lower than the climatology of all samples, TCCs formed in monsoon environments have larger sizes, lower brightness temperatures, longer lifetimes, and higher GPIs than those of TCCs formed in easterly environments. However, for TCCs formed in easterly environments, the average GPI for those TCCs that later develop into TCs (developing TCCs) is higher than that for other TCCs (nondeveloping TCCs). This difference is nonsignificant for TCCs formed in monsoon environments. Conversely, the average magnitudes of GPI are similar for developing TCCs, regardless of whether TCCs form in easterly or monsoon environments. In summary, the probability of a TCC to develop into a TC is more sensitive to the environmental conditions for TCCs formed in easterly environments than those formed in monsoon environments.

Evaluation and Error Analysis of Official Forecasts of Tropical Cyclones during 2005–14 over the Western North Pacific. Part I: Storm Tracks

Abstract Official forecasts of tropical cyclone (TC) tracks issued by the China Meteorological Administration (CMA); the Regional Specialized Meteorological Centre in Tokyo, Japan; and the Joint Typhoon Warning Center (JTWC) were used to evaluate the accuracies, biases, and trends of TC track forecasts during 2005–14 over the western North Pacific. Overall, the JTWC demonstrated the best forecasting performance. However, the CMA showed the most significant rate of improvement. Two main zones were discovered in the regional distribution of forecast errors: a low-latitude zone that comprises the South China Sea and the sea region east of the Philippines, and a midlatitude zone comprising the southern Sea of Japan and the sea region east of Japan. When TCs moved into the former zone, there were both translational speed and direction biases in the forecast tracks, whereas slow biases were predominated in the latter zone. Twelve synoptic flow patterns of TCs with the largest error have been identified based on the steering flow theory. Among them, the most two common pattern are the pattern with the combination of cyclonic circulations, subtropical ridges, and midlatitude troughs (CRT, 26 TCs), and the pattern of the TCs’ track that cannot be explained by steering flow (NSF, 6 TCs). In the CRT pattern, TCs move northwestward forced by the cyclonic circulations and the subtropical ridges and then turn poleward and eastward under the influence of the midlatitude troughs. In the NSF pattern, storms embedded in the southwest flow by the cyclonic circulation and the steering flow suggest TCs should turn to the right and move northeastward but instead TCs persisted in moving northwestward.

Quantification of the response of global terrestrial net primary production to multifactor global change

Based on an updated and comprehensive global NPP database, an artificial neural network (ANN) data mining approach was used to investigate the spatial and temporal patterns and control factors on global terrestrial ecosystem NPP between 1961 and 2010. Five variables (precipitation, air temperature, leaf area index, fraction of photosynthetically active radiation and atmospheric CO2 concentration) were selected and integrated to develop a three-layer back-propagation (BP) ANN model. The results indicated that the ANN method is capable of simulating and predicting the NPP of the global terrestrial ecosystem, yielding a simulation accuracy of 0.72 and a prediction accuracy of 0.60. The estimated global mean annual NPP was approximately 61.46PgC between 1961 and 2010, with an annual increase of 0.23PgC and a total increasing of 10.14PgC. The middle and high latitudinal zones made the major contribution to the total NPP increasing with percentage of 87.5% (8.87PgC), whereas the low latitude zone made the remaining contribution (1.27PgC). The atmospheric CO2 concentration was found to be the dominant factor that controlled the interannual variability and to be the major contribution (45.3%) of global NPP. Leaf area index, climate and fraction of photosynthetically active radiation resulted in NPP increases of 21.8%, 18.3% and 14.6%, respectively. Overall, multiple factors jointly control the variation in global NPP, and it is vital to consider the underlying mechanisms of combined environmental effects on NPP in future studies.

Spatial variations of methane absorption on Jupiter according to the results of quasicontinuous CCD spectrophotometry

Spectrophotometry observations of Jupiter were carried out during four nights in November–December 1999. Three hundred and eighty eight CCD-spectrograms of the central meridian of the planet were obtained and processed with doubly overlapped longitudes with a step of 1.8°. Latitudinal variations in central depths of methane absorption bands were studied corresponding to the wavelengths of 619, 725, 798, and 887 nm. It has been shown that these variations are mainly present at all longitudes, but for different absorption bands the positions of maxima and minima do not coincide. Zonal differences do not correlate with positions of dark and bright cloud belts in absorption, with one exception for the band 887 nm, which for a long time shows a well-expressed minimum in the equatorial zone of Jupiter. The 798 nm band reveals great dispersion of the depths at low latitudes as compared to other bands, which can be related with the presence of the ammonium absorption band. Comparison of the latitudinal absorption band variability at wave-lengths 619 and 725 nm shows a “loop-like” form of the relation between the depths of these bands in the low-latitude zone of Jupiter. Indicative estimates of the effective optical depth formation and absorption and their difference in the framework of simple two-layer model indicate the existence of vertical heterogeneity of the cloud cover varying with latitude.

Some properties of latitude-time evolution of local and background solar magnetic fields

A comparative analysis of evolution of latitude distributions of solar magnetic fields of various scales is presented.Using the local photospheric magnetic fields (LMF) represented by the magnetic fields of sunspots for cycles 12–23 it is found that the width of the sunspot generating zone is closely related to the magnitude of the total magnetic flux of sunspots. It is demonstrated that latitude-time distributions of the LMF and absolute strengths of the background magnetic field (BMF) in the latitude range ±40° are very similar and the time variations of power indices of the BMF and LMF are highly correlated. It is found that power characteristics of the BMF and LMF in cycles 21–23 are in close relation to the size of the low-latitude zone of solar activity.It is shown that the speed of the polar drift of the BMF of a given polarity tends to increase in epochs of solar cycle maximums.The obtained regularities can be used as diagnostic criteria for determination of adequate physical models of solar cyclicity.

Characterization of ionospheric GPS Total Electron Content (GPS–TEC) in low latitude zone over the Kenyan region during a very low solar activity phase

The ionosphere Total Electron Content (TEC), derived by analyzing dual frequency signals from the Global Positioning System (GPS) recorded from two stations in the Kenyan region is studied. We present the mean diurnal, monthly, seasonal, and annual variation in the ionospheric TEC during the lowest solar activity phase for the periods of 2009–2010. Seasonal variations in daytime TEC show a semiannual periodicity, with minimum in June solstice and maxima in March equinox and December solstice. Using mean hourly monthly TEC, we found semiannual variation with two maxima occurring in months of April–March, and September–October. Seasonal variations in the nighttime TEC reveal semiannual periodicity with high background levels observed in the equinoctial months and low background levels in solstice. Results of seasonal variations and month-to-month variations in TEC have been compared with the TEC derived from the IRI-2007 model using the NeQuick option for the topside electron density. The IRI–TEC is too high for all the seasons except for the March equinox where there seems to be good agreement between observation and model. The model is in good agreement with the monthly variation but overestimates for the months of May, June, July, August and September for all the years studied. The minimum monthly mean is lowest in the model for all the months by about 3–5 TECU in comparison to the GPS–TEC. We attribute this to the fact that the model excludes TEC from the plasmasphere while the overestimation of TEC has been associated to overestimation of the equatorial ion fountain effect and also the inability of the model to predict localized (regional) ionospheric effects arising from electromagnetic forcing at the low latitude.

Spectacular low- and mid-latitude electrical fields and neutral winds during a superstorm

In November 2004, a major magnetic storm occurred, a lengthy portion of which was recorded by the Upper Atmospheric Radar Chain. On the 9th and 10th, the Jicamarca Radar detected the highest magnitude penetrating electric fields (±3 mV/m) and vertical drifts (±120 m/s) ever seen at this premiere facility. These large and variable drifts were highly correlated with the interplanetary magnetic and electric fields and created a double F layer on the dayside and unusual TEC behavior throughout the low-latitude zone. These solar wind-induced drifts both suppressed and generated irregularities at the magnetic equator at different times. Large-scale thermospheric disturbances were generated by high-latitude heating and tracked through the middle- to low-latitude zones where both parallel and perpendicular plasma drifts created major ionospheric changes. The auroral oval was located at a magnetic L shell of about three for many hours.

Examination of Biomass Production by Afforestation Technologies in Arid Land of Low-Latitude Zone

Examination of Biomass Production by Afforestation Technologies in Arid Land of Low-Latitude Zone

The Quaternary Pan‐lake (Overflow) Period and Paleoclimate on the Qinghai‐Tibet Plateau

Abstract Lake geomorphology and high‐level lacustrine deposits since the mid‐late Pleistocene are well preserved in lakes of the Qinghai‐Tibet Plateau. According to geological surveys of 17 lake districts in different locations of the plateau, combined with interpretations of satellite images and topographic maps, the authors studied the timing of formation and scopes of the pan‐lake areas of the plateau and their paleoclimate. The latest two high lake levels (overflow surfaces) on the Qinghai‐Tibet Plateau in the Quaternary occurred at ∼40 to 30/35 ka and ∼65 to 53 ka respectively. In these time intervals, the plateau was covered by huge interconnected pan‐lake systems with a total area of ∼36000km2 and a total volume of lake water of &gt;530 million km2, which are about 38 times and 659 times larger than those of the modern lakes respectively. Before this pan‐lake period in the late Pleistocene, there had been three high lake levels that occurred at ∼132–112 ka, 110–95 ka and 91–72/∼83–75 ka respectively, suggesting that the late Quaternary climate on the plateau was unstable and changed rapidly. The ∼40–30 ka high lake level also appeared in the Tengger desert north of the plateau, suggesting that there existed very strong summer monsoons from South Asia then; the variation in solar radiation with a 20,000 precessional period has special importance for the high‐altitude Qinghai‐Tibet Plateau in the low‐latitude zone of the Earth. Around 30 ka, the pan‐lakes at the peripheries of the Qinghai‐Tibet Plateau drained out suddenly with rapid uplift of the plateau and cooling. In a short time the huge amount of cold lake water emptied into the Indian Ocean and Western Pacific. The draining event of the pan‐lakes brought about the environmental changes of rivers and lakes at peripheries of the plateau.

Solar magnetic fields and the intensity of the green coronal line

Synoptic maps of the intensity of the λ530.5 nm FeXIV green coronal line and maps of computed coronal magnetic fields for the period 1977–2001 are compared. For quantitative comparisons, the correlation coefficients r for the correlation between these two parameters at corresponding points of the synoptic maps are calculated. This coefficient exhibits cyclic variations in the spot-formation zone, ±30° and the zone above 30° and is in antiphase in these two zones. In the low-latitude zone, the correlation coefficient is always positive, reaches its maximum at activity minimum, and strongly decreases by activity maximum. Above 30°, r reaches maximum positive values at activity maximum and then gradually decreases, passing through zero near the beginning of the phase of activity minimum and becoming negative during this phase. A Fourier analysis of r as a function of time reveals a wavelike variation with a period close to 1.3 yr (known also from helioseismological data for the tachoclinic region of magnetic-field generation), as well as a pronounced wave with a period of about 5 yr. The latitude dependence of r seems to be related to variations in the contributions from local, large-scale, and global fields. Our analysis suggests an approach to studying the complex problem of mechanisms for coronal heating.

Comparison of anthocyanin accumulation and morpho-anatomical features in apple skin during color formation at two habitats

Differences in anthocyanin accumulation and morpho-anatomical features in skin of apple cultivars ( Malus domestica Borkh cv. Starkrimson and Golden Delicious) were compared during the color formation at two habitats (Maoxian and Ya’an, China) in the low latitude zone of apple cultivation. Anthocyanin content in the skin of both cultivars under the semi-arid, cool, and high-irradiant habitat of Maoxian was higher than that under the moist, warm, and low-irradiant habitat of Ya’an. Likewise, the contents of reducing and non-reducing sugar, and the activity of phenylalanine ammonia-lyase (PAL, E.C.4.3.1.5) were also higher, but contents of malic acid and water were lower in skin of the two cultivars of Maoxian. Within the same habitat, higher content of anthocyanin and activity of PAL were found in skin of ‘Starkrimson’ apple than ‘Golden Delicious’ apple, but no difference in the contents of reducing and non-reducing sugar, malic acid, and water. The analysis of morphological and anatomical features showed that the two apple cultivars in Maoxian had smaller and fewer lenticels, thicker cuticle, longer and thinner epidermal cells, and longer and thinner sub-epidermal cells with more layers than those in Ya’an. Regression analysis showed that PAL activity, reducing sugar content, and lenticel density, as well as cuticular thickness, and cell length and thickness of epidermis, were associated with anthocyanin accumulation in apple skin.