Tropical Montane Cloud Forests (TMCFs) form biodiverse communities that are characterized by frequent occurrence of low-level clouds from which they capture a substantial proportion of their precipitation — here referred to as occult precipitation. TMCFs provide important ecosystem services, in particular the supply of water to their wider surroundings. Throughout the tropics (here 23.5^∘ S to 23.5^∘ N), they are under pressure from deforestation and poor land management which leads to loss of both forest area and species diversity, and reduces their capture of occult precipitation. Climate change may also reduce occult precipitation in TMCFs since the cloud base may lift in response to higher temperatures — the ‘lifting cloud-base hypothesis’. These threats to TMCFs are well understood, but their quantitative assessment is hampered by 1) uncertainty in the location and spatial extent of TMCFs and 2) limited availability of representative meteorological data. We use a Random Forest Classifier — informed by topographic data, MODIS vegetation data, TRMM precipitation data and ERA5-Land and MERRA-2 reanalysis products — to estimate the spatial distribution and extent of TMCFs (2.1 × 10⁶ km² ± 0.5 × 10⁶ km²). We analyze temporal changes in climate, tree-cover and greenness of TMCFs over the past two to four decades to detect 1) multi-decadal trends, and 2) associations with the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Evidence for the ‘lifting cloud-base hypothesis’ in reanalysis products was inconsistent across the tropics; a lifting of the cloud base during the past four decades occurred for about 20% of TMCFs, predominantly in the Americas and a few locations in Africa, while in Asia a downward movement of the cloud base was found. However, these results in part depend on the bias correction applied to the reanalyses. Changes in TMCF tree cover and greenness varied by continent; in Africa in 50% of TMCFs tree cover declined, whereas TMCFs in the Americas and in Asia exhibited a net increase in tree cover, despite a reduction in tree cover in ~20% of these TMCFs. An important limitation of the tree-cover data is that they do not distinguish between natural tree cover and agro-forestry. ENSO signals were more strongly present in precipitation in American and Asian TMCFs, whereas IOD signals were stronger in TMCF temperature and dewpoint temperature across the tropics. ENSO and IOD signals were approximately equally important for precipitation in African TMCFs and in cloud-base height across the tropics. An arbitrary warming of 1 ^∘C and a 100 m lifting of the cloud base, in accordance with the ‘lifting cloud hypothesis’, imposed on the Random Forest classifier showed a decline in the extent of TMCFs in the Americas and Africa, but an increase in Asia — mostly at the expense of evergreen broadleaf forests. The greater vulnerability of TMCFs in Africa may be linked to their more isolated and scattered distribution across the continent and drier conditions compared to a more continuous distribution and wetter conditions in the Americas and Asia.

热带山地云雾森林（TMCF）形成了生物多样性群落，其特征是经常出现低层云，它们从中捕获了很大一部分降水（这里称为隐性降水）。TMCF提供重要的生态系统服务，尤其是向其更广阔的环境供水。在整个热带地区（此处为^23.5∘S至^23.5∘N），它们正遭受毁林和土地管理不善的压力，导致森林面积和物种多样性的丧失，并减少了对隐性降水的捕获。气候变化也可能减少TMCF的隐匿降水，因为云层的底部可能会随着温度升高而升高，这就是“云层顶部的假设”。对TMCF的这些威胁已广为人知，但1）TMCF的位置和空间范围的不确定性和2）代表性气象数据的可用性有限，阻碍了它们的定量评估。我们使用随机森林分类器（根据地形数据，MODIS植被数据，TRMM降水数据以及ERA5-Land和MERRA-2再分析产品），估算了TMCF的空间分布和范围（2.1×10 ⁶ km ²±0.5×10 ⁶公里²）。我们分析了过去两到四十年中TMCF的气候，树木覆盖和绿色的时间变化，以发现1）十年的趋势，以及2）与厄尔尼诺南方涛动（ENSO）和印度洋偶极子（IOD）的关联。重新分析产品中“基于云的假说”的证据在整个热带地区并不一致。在过去的40年中，约有20％的TMCF发生了云基础的抬高，主要发生在美洲和非洲的一些地方，而在亚洲，云基础的向下移动。但是，这些结果部分取决于应用于重新分析的偏差校正。TMCF树木覆盖率和绿色度的变化因大陆而异；在非洲，有50％的TMCF树木覆盖率下降了，而在美洲和亚洲，TMCF的树木覆盖率出现了净增长，尽管这些TMCF的树木覆盖率减少了约20％。树木覆盖率数据的一个重要局限性在于它们无法区分自然树木覆盖率和农林业。在美洲和亚洲TMCF中，ENSO信号在降水中更强，而热带地区TMOD温度和露点温度中的IOD信号较强。ENSO和IOD信号对于非洲TMCF和热带地区云基高度的降水具有同等重要的意义。任意升温1 而在热带地区，TMD温度和露点温度的IOD信号较强。ENSO和IOD信号对于非洲TMCF和热带地区云基高度的降水具有同等重要的意义。任意升温1 而在热带地区，TMD温度和露点温度的IOD信号较强。ENSO和IOD信号对于非洲TMCF和热带地区云基高度的降水具有同等重要的意义。任意升温1^∘ C和云底的百米起重，在按照“提升云假说”，施加在随机森林分类显示在TMCFs在美洲和非洲的程度的下降，但是增加了亚-主要是在常绿阔叶林的代价。与美洲和亚洲更连续的分布和湿润的条件相比，非洲TMCF更大的脆弱性可能与其在整个大陆和更干燥条件下更孤立和分散的分布有关。