Land use changes exert important impacts on climate, primarily through altering greenhouse gas (GHG) and surface energy fluxes. Biogeochemical models have incorporated a relatively complete suite of biogeochemical processes to simulate GHG fluxes. However, these models often lack detailed processes of surface energy exchange, limiting their ability to assess the impacts of land use change on climate. In this study, we incorporated processes of surface energy exchange into a widely used biogeochemistry model, DeNitrification‐DeComposition (DNDC), so that it can quantify both GHG and energy fluxes between the biosphere and the atmosphere. When tested against field observations for the three dominant land use types (forest, hayfield, and cornfield) in the northeastern United States, the improved DNDC successfully captured the observed fluxes of outgoing shortwave radiation, latent heat, sensible heat, net ecosystem exchange of CO₂, and their differences among the three land use types. To evaluate the differences in radiative forcing among these land use types, we conducted 100‐year simulations and converted the modeled GHG fluxes to radiative forcing using an atmospheric impulse response model. Our results show that the 100‐year cumulative differences in net radiative forcing are 3.35 nW m⁻² between the hayfield and forest (slight warming) and 43.2 nW m⁻² between the cornfield and forest (warming) per hectare land use difference. The cooling effects of increased albedo after the conversion of forest to hayfield or cornfield (observed and modeled in recent years) are gradually offset by the warming effects of the increasing release of GHG as the forest becomes older.

中文翻译：

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改进生物地球化学模型以模拟美国东北部不同土地利用类型的表面能，温室气体通量和辐射强迫

土地利用变化主要通过改变温室气体（GHG）和表面能通量，对气候产生重要影响。生物地球化学模型已经纳入了一套相对完整的生物地球化学过程，以模拟温室气体通量。但是，这些模型通常缺乏详细的地表能量交换过程，从而限制了它们评估土地利用变化对气候影响的能力。在本研究中，我们将表面能交换过程纳入了广泛使用的生物地球化学模型“脱氮-分解”（DNDC）中，以便可以量化生物圈与大气之间的温室气体和能量通量。在针对美国东北部三种主要土地利用类型（森林，干草田和玉米田）的实地观察进行测试时，₂，以及三种土地利用类型之间的差异。为了评估这些土地利用类型之间的辐射强迫差异，我们进行了100年的模拟，并使用大气脉冲响应模型将模拟的GHG通量转换为辐射强迫。我们的结果表明，每公顷土地利用差异中，干草地和森林之间的100年累积累积辐射差异为3.35 nW m ^-2（略微变暖），而玉米田和森林之间的净辐射强迫（增温）为43.2 nW m ^-2（变暖）。随着森林的变老，GHG释放量增加的变暖效应逐渐抵消了森林向干草田或玉米田转化后反照率增加的降温效果（近年来观察和模拟）。