Modeling the impacts of grazing land management on land-use change for the Jordan River region

In this article, we describe a simulation method for investigating the impacts of different grazing land management strategies on the productivity of (semi-)natural vegetation and the resulting feedback on land-use change. In a first application, we analyze the effects of sustainable and intensive grazing land management in the Jordan River region. For this purpose, we adapt and use the regional version of the spatially explicit modeling framework LandSHIFT. Our simulation experiments indicate that the modeled feedback mechanism has a strong effect on the spatial extent of grazing land. Consequently, the results of our study underline that the inclusion of such feedback mechanisms in land-use models can help to represent and analyze the complex interactions between humans and the environment in a more differentiated and realistic way, but they also identify the demand for more detailed empirical data on grazing land degradation in order to further improve the explanatory power of the model.     

Validation of a multidecadal RCM hindcast over East Asia

The precipitation and low-level air temperature in East Asia from a regional climate model (RCM) hindcast for the 22-year period 1979–2000 is evaluated against observational data in preparation for the model use in regional climate change research. Emphasis of the evaluation is placed on the RCM capability in capturing the temporal and spatial variability of precipitation and low-level temperature, especially in conjunction with important climatological events such as, ENSO and East Asian monsoon, at three spatial scales of continental, subcontinental, and river basins.Spatial anomaly correlation time series of geopotential height and temperature show that the simulated upper-air fields remain consistent with the driving large-scale fields, NCEP Reanalysis 2 (R2), throughout the period. The simulated seasonal shifts in 850 hPa winds also agree well with R2 over eastern China and the western Pacific Ocean although the magnitudes of the shifts are overestimated, especially over the eastern slope of the Tibetan Plateau and in northern Manchuria. The simulated precipitation climatology agrees reasonably with that from two analysis datasets based on station- and remote-sensing data. Outstanding characteristics of precipitation including the location of the main rainband, climatological means, and the spatiotemporal variability in association with East Asian Monsoon, ENSO, and extreme events, are well represented in the hindcast. The most notable bias in the simulated precipitation is an overestimation of winter rainfall in southwestern coast of China, near the border with Vietnam. The simulation overestimates the interannual variability of seasonal precipitation especially in southern China, however, the corresponding coefficients of variation agree reasonably with observations except in very dry regions. This suggests that climate sensitivity of scaled precipitation can be useful for projecting climate change signals. The simulated low-level temperature climatology agrees reasonably with observational data as well. The most noticeable biases in the simulated low-level temperature are the warm (cold) biases in southern Siberia (northeastern China) during winter (summer) and the systematic underestimation of low-level temperature in the Tibetan Plateau for all seasons. The daily maximum temperature is underestimated for all seasons by 2−3 K with the largest biases in spring and fall except in the northwestern Mongolia region where it has been overestimated during winter. The daily minimum temperature biases ranges from 0.3 K in spring to 2 K in winter, and are much smaller than those in daily maximum temperature. The evaluation of the multidecadal hindcast shows that model errors mostly confined in the region near the lateral boundaries of the model domain with only minor biases in eastern China. This allows us to be cautiously optimistic about the RCM usefulness for studies of precipitation and low-level temperature changes in East Asia induced by increased emissions of greenhouse gases.     

Scenarios of land cover in China

A method for surface modeling of land cover change (SMLC) is developed on the basis of establishing transition probability matrixes between land cover types and HLZ types. SMLC is used to simulate land cover scenarios of China for the years 2039, 2069 and 2099, for which HLZ scenarios are first simulated in terms of HadCM3 climatic scenarios that are downscaled in zonal model of spatial climate change in China. This paper also analyzes spatial distribution of land cover types, area change and mean center shift of each land cover type, ecotope diversity, and patch connectivity under the land cover scenarios. The results show that cultivated land would decrease and woodland would expand greatly with climatic change, which coincides with consequences expected by implementation of Grain-for-Green policy. Nival area would shrink, and desertification area would expand at a comparatively slow rate in future 100 years. Climate change would generally cause less ecotope diversity and more patch connectivity. Ecosystems in China would have a pattern of beneficial cycle after efficient ecological conservation and restoration. However, if human activities would exceed regulation capacity of ecosystems themselves, the ecosystems in China might deteriorate more seriously.     

Modelling the impacts of environmental changes on hydrological regimes in the Hei River Watershed, China

This study aimed to disclose impacts of environment changes on hydrologic regimes in the Hei River Watershed, Shaanxi Province in China. We investigated the effects of the man-made landscape (Jingpen Reservoir) on the rainstorm–flood processes using a proposed Kinematic Wave model, simulated impacts of land use and cover changes on surface runoff generation and river flow characteristics at monthly, seasonal, and annual scales through designed scenarios of different combinations of land use and cover and climate conditions on basis of the SWAT model, evaluated the climate change and human activities effects on water balance from 1954 to 2001. Through these investigations, the following results were achieved. Firstly, it showed that the man-made landscape (the Jingpen Reservoir) had altered the rainstorm–flood process, the flood wave damped right after it flowed out the Jingpen Reservoir. Secondly, changes of land use and cover led to river flow redistribution, soil moisture and recharge fluctuations. Evapotranspiration increased 12.9%, river flow discharge decreased 17.7%, runoff generation process accelerated 1.31 times in 2000 than in 1986, and water resources of the total watershed decreased 7.7% in 2000 compared to the land use and cover scenario in 1986. Finally, the interaction between climate change and human activities led to the total water resource decreased by 10.6% in 2000 compared to that in 1986 in the Hei River Watershed.     

A comparison of simulated monsoon circulations and snow accumulation in Asia during the mid-Holocene and at the Last Glacial Maximum

Tropical climatology through the last glacial cycle is believed to have ranged from colder, windier conditions at the Last Glacial Maximum (LGM) to relatively warm, stable conditions during the Holocene. Changes in strength of the South Asian monsoon have previously been determined from a variety of proxy data and have been attributed primarily to changes in radiative forcing, although tropical sea surface temperature (SST) is known to play a fundamental role in regulating monsoon strength and is also believed to have changed throughout the late Quaternary.In this study, the monsoons simulated in a coupled atmosphere–ocean general circulation model (GCM) configured for the mid-Holocene (6000 years B.P.) and for the LGM (21,000 years B.P.) are compared. The colder and windier conditions simulated for the LGM produced a summer monsoon whose westerly winds are stronger and whose precipitation and snowfall into the eastern Himalaya are increased, with drier conditions over the rest of the Indian subcontinent and over most of southwest Asia.The mid-Holocene monsoon circulation is stronger than today, and annual mean snow accumulation is increased over the northwestern Himalaya. These changes in precipitation and snow accumulation are analyzed in terms of the altered atmospheric circulations, which are in turn driven by changes in radiative forcing, sea surface temperatures, and sea surface height. All of these factors are therefore demonstrated to be important in governing the spatial distribution of snow and ice deposition in the Himalaya during the late Quaternary, and are likely to have contributed to the observed asynchroneity of Himalayan glaciation and Northern Hemisphere ice sheet volume.     

Denudation and uplift history of the Jameson Land basin, East Greenland—constrained from maturity and apatite fission track data

The Jameson Land basin in East Greenland comprises a well exposed succession of Upper Paleozoic–Mesozoic sediments. During Middle Devonian–Early Permian rifting, 13 km of continental clastics were deposited. In latest Paleozoic to Mesozoic times, 4 km of sediments accumulated during regional subsidence. In the Early Paleocene, during North Atlantic break-up, the basin was covered by a thick volcanic pile. Subsequently, uplift and erosion took place over the whole region. The volcanic cover was completely removed from Jameson Land and erosion cut deeply into the underlying sediments. To assess the exploration potential of Jameson Land, a basin modelling study with 21 1D pseudo-wells was carried out based on all seismic and surface data available. In addition to the calculation of hydrocarbon generation in space and time, the basin modelling provided an opportunity to study the magnitude and timing of uplift and erosion. Basin modelling constrained by apatite fission track data has made it possible to determine a consistent uplift and erosion history of the area. Tectonic backstripping based on a simple Airy type isostatic model has been used to separate the tectonic uplift from the actual uplift. The combined basin modelling and backstripping study has led to the following conclusions: (1) the thickness of the Cretaceous succession varied from 1.3 km in the south to 0.3 km in the north; (2) the volcanic rocks formed a wedge with a thickness of >2 km in the south thinning to <0.1 km in the north; (3) the subsequent erosion of 2–3 km is in response to tectonic uplift with a magnitude of 1 km, and the calculated tectonic uplift shows increasing values to the north. The erosion rate generally accelerated from Late Paleocene up to the present time.     

Geochemical composition of inner shelf Quaternary sediments in the northern South China Sea with implications for provenance discrimination and paleoenvironmental reconstruction

Sediment samples were collected from a borehole in the northern South China Sea with the depositional age back to 400 ka BP, for grain size and geochemical analyses to constrain the sediment provenance and paleoenvironmental variability. Geochemical indices of Th/Sc, Ti/Nb and Th/Nb ratios suggest that the Zhujiang (Pearl River) was the main provenance of the inner shelf sediments of Hong Kong deposited during interglacial periods, whereas the locally-derived granitoids contributed significantly to the exposed inner shelf through the incision of local streams during glacial periods. Furthermore, the influence of the Zhujiang-derived sediments on the inner shelf of Hong Kong varied spatially and temporally with different sea-level changes during the past 400 kyr. Chemical weathering indices suggest hot and wet climate conditions were dominant in South China during interglacial periods of marine isotope stages (MIS) 7, 9 and 11 whereas a dry and cold paleoclimate prevailed during glacial periods of MIS 6 which accounts for weak chemical weathering and coarse-grained deposition on the inner shelf. The Holocene and last interglacial period did not see more intense chemical weathering in the Zhujiang drainage basin than other interglacial periods. Although the high resolution paleoenvironmental changes can not be easily reconstructed due to ubiquitous unconformity in the sedimentary strata and weak age controls compared to the deep sea sedimentation, the present study sheds new lights on the understanding of the transport process of the Zhujiang sediment in the deep ocean and provides a teleconnection of East Asian palaeomonsoon activity between South China, the inland and open sea areas.     

Coral Sr/Ca and Mg/Ca records in Con Dao Island off the Mekong Delta: Assessment of their potential for monitoring ENSO and East Asian monsoon

The climate of the South China Sea (SCS) is dominated by the East Asian monsoon (EAM) and can be related to the El Niño-Southern Oscillation (ENSO) owing to the interaction between ENSO and the EAM. An annually-banded coral (Porites sp.) collected from Con Dao Island in the southern SCS was measured for Sr/Ca and Mg/Ca ratios at near-monthly resolution through the annual bands of AD 1948–1999. This island is only ~ 90 km from the Mekong Delta coast and thus significantly influenced by riverine discharge, suggesting relatively severe environmental stress on corals. The Sr/Ca time series shows a clear annual cyclicity chiefly modulated by sea-surface temperature (SST), whereas the Mg/Ca time series exhibits an indistinct annual cyclicity, indicating that the previously-proposed coral Mg/Ca thermometry is greatly disturbed. An instrumental SST record in Con Dao Island (since 1980) has been compared with the Sr/Ca time series to calibrate a Sr/Ca thermometer. The Sr/Ca vs. SST comparison shows that the Sr/Ca thermometer is sometimes disturbed by some factor and that almost all of the disturbances occur around the annual-maximum SST in the warm/wet season. The Sr/Ca data around the annual-minimum SST in the cool/dry season is almost free from the disturbance and thus useful as a SST proxy. The disturbances of the Sr/Ca and Mg/Ca thermometers may be ascribed to the Mekong River discharge and its accompanying phenomena (i.e., large freshwater input, suspended-sediment loads, intense phytoplankton blooms, etc.), which are likely to disturb coral physiological processes. Applying the Sr/Ca thermometer to the whole Sr/Ca time series provides a SST reconstruction from 1948 through 1999. Reconstructed annual-minimum SSTs show a clear quasi-biennial oscillation significantly correlated with ENSO, indicating that the annual-minimum SST in the southern SCS tends to be higher (lower) in El Niño (La Niña) phases. This is compatible with previous observations that the East Asian winter monsoon is weakened (strengthened) in El Niño (La Niña) phases. The reconstructed SST record suggests a warming of 1.0 °C for the latter half of the 20th century. The Sr/Ca and Mg/Ca time series exhibit similar decadal-to-bidecadal variations, which do not seem to be primarily due to SST variability but rather due to some other factor possibly related to disturbance or fluctuation of coral physiological processes. Although both of our Sr/Ca and Mg/Ca data are affected, to a greater or lesser extent, by some non-temperature factor, a part of the Sr/Ca data provides a useful SST proxy and suggests that coral-based SST reconstruction in the southern SCS may be an effective means for monitoring the EAM and ENSO.     

Simulations of the impacts of dynamic vegetation on interannual and interdecadal variability of Asian summer monsoon with modern and mid-Holocene orbital forcings

The impacts of dynamic vegetation on interannual and interdecadal variability of Asian summer monsoon in modern (0 kyr) and mid-Holocene (6 kyr) climates are investigated by contrasting simulations with and without dynamic vegetation in a coupled ocean-atmosphere model.According to a dynamic index of South Asian summer monsoon, it has been found that the strengths of interannual and interdecadal westerly wind tend not to be affected by the dynamic vegetation over South Asia in the lower troposphere for 0 kyr and 6 kyr. However, based on a dynamic index of western North Pacific (WNP) monsoon, the strengths of tropical westerly wind and south–north cross-equatorial transport are weakened over the tropical western Pacific in the lower troposphere for 0 kyr and 6 kyr. It suggests the impact of dynamic vegetation is more obvious for the WNP monsoon than for the South Asian monsoon. Also, it implies the impact of dynamic vegetation on the interannual and interdecadal circulations is distinctly regional.Singular value decomposition (SVD) analysis shows that the impact of dynamic vegetation can remodel the leading correlation mode (SVD1) between precipitation and surface temperature. All of the interannual and interdecadal precipitation patterns with and without the impact of dynamic vegetation are associated with positive anomalies over India and southeastern China. However, the impact of dynamic vegetation tends to enhance (keep) the positive interannual temperature anomalies of SVD1 over the midlatitudinal Eurasia (WNP) for 0 kyr, but to reduce the anomalies over the midlatitudinal Eurasia and WNP for 6 kyr. Furthermore, the La Niña-like sea surface temperature (SST) anomalies always dominate the tropics for 0 kyr and 6 kyr. It suggests La Niña-like SST anomalies are the important mechanism to induce the above-mentioned precipitation pattern no matter whether for 0 kyr or for 6 kyr. For the interdecadal surface temperature pattern of SVD1, the impact of dynamic vegetation tends to enhance (reduce) positive anomalies over the midlatitudinal Eurasia (WNP) for 0 kyr, but to reduce (keep) positive anomalies over the midlatitudinal Eurasia (WNP) for 6 kyr. Also, all of the above implies the impact of dynamic vegetation is a mechanism to induce the long-term change of leading interannual and interdecadal surface temperature pattern over the midlatitudinal Eurasia and/or WNP.     

Simulations of the impact of orbital forcing and ocean on the Asian summer monsoon during the Holocene

The importance of orbital forcing and ocean impact on the Asian summer monsoon in the Holocene is investigated by comparing simulations with a fully coupled ocean–atmosphere general circulation model (FOAM) and with the atmospheric component of this model (FSSTAM) forced with prescribed modern sea-surface temperatures (SSTs). The results show: (1) the ocean amplifies the orbitally-induced increase in African monsoon precipitation, makes somewhat increase in southern India and damps the increase over the southeastern China. (2) The ocean could change the spatial distribution and local intensity of the orbitally-induced latitudinal atmospheric oscillation over the southeastern China and the subtropical western Pacific Ocean. (3) The orbital forcing mostly enhances the Asian summer precipitation in the FOAM and FSSTAM simulations. However, the ocean reduces the orbitally-induced summer precipitation and postpones the time of summer monsoon onset over the Asian monsoon region. (4) The orbital forcing considerably enhances the intensity of upper divergence, which is amplified by ocean further, over the eastern hemisphere. But the divergence is weaker in the FOAM simulations than in the FSSTAM simulations when the orbital forcing is fixed. (5) The orbital forcing can enhance the amplitude of precipitation variability over the subtropical Africa, the southeastern China and northwestern China, inversely, reduce it over central India and North China in the FOAM and FSSTAM simulations. The ocean obviously reduces the amplitude of precipitation variability over most of the Asian monsoon regions in the fixed orbital forcing simulations. (6) The areas characterized by increased summer precipitation in the long-term mean are mostly characterized by increased amplitude of short-term variability, whereas regions characterized by decreased precipitation are primarily characterized by decreased amplitude of short-term variability. However, the influences of orbital forcing or dynamical ocean on regional climate depend on the model.     

An empirical assessment of the impact of climate change on smallholder agriculture in Cameroon

Rainfed tropical agriculture provides important avenue to ascertain the consequences of climate change. This is because reliability of rainfall accounts for much of the variation in agriculture in the region. In addition, the region is already hot and vulnerable from further warming. This study shows from a climate change experiment using Ricardian method in Cameroon that a 7% decrease in precipitation would cause net revenues from crops to fall US$2.86 billion and a 14% decrease in precipitation would cause net revenue from crops to fall US$3.48 billion. Increases in precipitation would have the opposite effect on net revenues. For a 2.5 °C warming, net revenues would fall by US$0.79 billion, and a 5 °C warming would cause net revenues to fall US$1.94 billion. This highlights that agriculture is not only limited by seasonality and magnitude of moisture availability, but also it is significantly impacted by climate change.     

The effect of climate change on carbon in Canadian peatlands

Peatlands, which are dominant features of the Canadian landscape, cover approximately 1.136 million km², or 12% of the land area. Most of the peatlands (97%) occur in the Boreal Wetland Region (64%) and Subarctic Wetland Region (33%). Because of the large area they cover and their high organic carbon content, these peatlands contain approximately 147 Gt soil carbon, which is about 56% of the organic carbon stored in all Canadian soils.A model for estimating peatland sensitivity to climate warming was used to determine both the sensitivity ratings of various peatland areas and the associated organic carbon masses. Calculations show that approximately 60% of the total area of Canadian peatlands and 51% of the organic carbon mass in all Canadian peatlands is expected to be severely to extremely severely affected by climate change.The increase in average annual air temperature of 3–5 °C over land and 5–7 °C over the oceans predicted for northern Canada by the end of this century would result in the degradation of frozen peatlands in the Subarctic and northern Boreal wetland regions and severe drying in the southern Boreal Wetland Region. In addition, flooding of coastal peatlands is expected because of the predicted rise in sea levels. As a result of these changes, a large part of the carbon in the peatlands expected to be severely and extremely severely affected by climate change could be released into the atmosphere as carbon dioxide (CO₂) and methane (CH₄), which will further increase climate warming.     

被动型氢钟流量变化对长期频率稳定度的影响分析

为提高系统的长期频率稳定度(它是被动型氢钟的一个重要指标),设计了一种实验,用以分析在不同微波腔谐振频率下,氢气流量变化对输出频率的影响。通过实验发现微波腔的控制电压存在一个调谐点,在调谐点附近,流量变化对输出频率的影响变小。但是对于单频系统,如何将微波腔锁定在调谐点附近以及如何减小流量的影响和提高系统的长期频率稳定度还需要进一步探索。     

Phytolith indices as proxies of grass subfamilies on East African tropical mountains

The main objective of this paper is to provide researchers that investigate fossil phytolith assemblages and model/data comparisons a new tool for estimating C₃/C₄ grass composition over time. We tested the reliability of modern soil phytolith assemblages and phytolith indices for tracing the dominance of different grass subfamilies and tree cover density. We analyzed modern soil phytolith assemblages from sites over elevation gradients on Mount Kenya (Kenya), Mount Rungwe and around Lake Masoko (southern Tanzania). These data were compared with available botanical data. A phytolith index named Ic, proved to be an effective proxy of the proportions of Pooideae, Arundinoideae and Bambusoideae grasses (mainly C₃ grasses) versus Panicoideae grasses (mainly C₄ grasses), increasing with elevation in East-Africa. When tropical mountains are covered by open habitats (e.g. grasses and shrublands), Ic should be a reliable proxy of the C₃/C₄ grass composition. These results highlight the value of the phytolith index Ic, when interpreting paleo-environmental records from tropical mountains, to: 1) better understand past local and regional C₃/C₄ grass distributions and associated climatic changes and 2) increase the set of C₃/C₄ data available for model/data comparisons.     

The economic impact of climate change on Kenyan crop agriculture: A Ricardian approach

This paper measures the economic impact of climate on crops in Kenya. We use cross-sectional data on climate, hydrological, soil and household level data for a sample of 816 households. We estimate a seasonal Ricardian model to assess the impact of climate on net crop revenue per acre. The results show that climate affects crop productivity. There is a non-linear relationship between temperature and revenue on one hand and between precipitation and revenue on the other. Estimated marginal impacts suggest that global warming is harmful for crop productivity. Predictions from global circulation models confirm that global warming will have a substantial impact on net crop revenue in Kenya. The results also show that the temperature component of global warming is much more important than precipitation. Findings call for monitoring of climate change and dissemination of information to farmers to encourage adaptations to climate change. Improved management and conservation of available water resources, water harvesting and recycling of wastewater could generate water for irrigation purposes especially in the arid and semi-arid areas.     

Effects of anthropogenic intervention in the land hydrologic cycle on global sea level rise

Recent studies suggest that anthropogenic modification of land hydrology (e.g. through groundwater mining, dam building, irrigation, deforestation, wetlands drainage, and urbanization) could significantly impact sea-level rise, although the magnitude and sign of this effect have been widely debated. This paper attempts a comprehensive overview of the effects of human activities on land hydrology. Estimates are provided for the volumes of water associated with each of the major anthropogenic processes and the corresponding equivalent in sea level.Groundwater mining; and runoff from paved and built-up areas are two major sources of water added to the ocean. In contrast, storage of water behind dams, losses through percolation, and evapotranspiration from irrigated fields withhold water that would otherwise flow to the sea. The net effect of these processes holds back the equivalent of 0.8 +- 0.4 mm/yr from sea-level rise. This is a magnitude comparable to, but in the opposite direction from the currently observed sea-level rise of 1–2 mm/yr. These estimates are still preliminary, awaiting better documentation. Coupling of improved land hydrology models with GCMs will help in analysis of feedbacks, especially the partitioning of water among runoff, infiltration, and evaporation.     

Measuring the economic impact of climate change on major South African field crops: a Ricardian approach

This study employed a Ricardian model to measure the impact of climate change on South Africa's field crops and analysed potential future impacts of further changes in the climate. A regression of farm net revenue on climate, soil and other socio-economic variables was conducted to capture farmer-adapted responses to climate variations. The analysis was based on agricultural data for seven field crops (maize, wheat, sorghum, sugarcane, groundnut, sunflower and soybean), climate and edaphic data across 300 districts in South Africa. Results indicate that production of field crops was sensitive to marginal changes in temperature as compared to changes in precipitation. Temperature rise positively affects net revenue whereas the effect of reduction in rainfall is negative. The study also highlights the importance of season and location in dealing with climate change showing that the spatial distribution of climate change impact and consequently needed adaptations will not be uniform across the different agro-ecological regions of South Africa. Results of simulations of climate change scenarios indicate many impacts that would induce (or require) very distinct shifts in farming practices and patterns in different regions. Those include major shifts in crop calendars and growing seasons, switching between crops to the possibility of complete disappearance of some field crops from some region.     

Postglacial relative sea-level change and stratigraphy of raised coastal basins on Kola Peninsula, northwest Russia

A relative sea-level curve for the Holocene is constructed for Polyarny on the Kola Peninsula, northwest Russia. The curve is based on 18 radiocarbon dates of isolation contacts, identified from lithological and diatomological criteria, in nine lake basins situated between 12 and 57 m a.s.l. Most of the lakes show a conformable, regressive I–II–III (marine–transitional–freshwater) facies succession, indicating a postglacial history comprising an early (10,000–9000 radiocarbon years BP) phase of rapid, glacio-isostatically induced emergence (5 cm year⁻¹) and a later phase (after 7000 years BP,) having a moderate rate of emergence (<0.5 cm year⁻¹). Three lakes together record a phase of very low rate of emergence or slight sea-level rise at a level of 27 m a.s.l., between 8500 and 7000 years BP, which correlates with the regional Tapes transgression. Pollen stratigraphy in the highest lake shows that the area was deglaciated before the Younger Dryas and that previously reconstructed Younger Dryas glacier margins along the north Kola coast lie too far north.     

Four climate regimes on a land planet with wet surface: Effects of obliquity change and implications for ancient Mars

Series of numerical experiments are performed using a general circulation model to gain insights on the hydrologic cycle on ancient Mars. Since the state of the ancient Mars atmosphere is not well constrained, we did not try to simulate an ancient Mars climate under warm and wet condition. In stead, we used an idealized model and tried to extract general features of the hydrologic cycle by modeling an ideal land planet that has no ocean on its surface. Four different climate regimes, “warm-upright,” “warm-oblique,” “frozen-upright,” and “frozen-oblique” regimes, are recognized depending on the inclination of the spin axis (obliquity) and average surface temperature. The period of active hydrologic cycle suggested from the geomorphology on Mars seems to be consistent with that at the “warm-oblique” regime, which appears at warm (above-freezing) environment with high-obliquity (higher than about 30°) condition.