Abstract ID: 3.13075 | Accepted as Talk | Talk/Oral | TBA | TBA

For 20 years we have collaborated with Peruvian research engineers and university students to maintain a low-cost array of embedded sensors logging hourly measurements of air temperature and humidity spanning ~1km vertically to a maximum elevation of 4700 m in the tropical Peruvian Andes. These sensors have been complemented by additional weather stations and provide a unique data set to examine patterns of elevation dependent changes in key climate variables. We observe greater rates of warming at higher elevations, with variability between wet and dry seasons. An upward trend in daily temperatures at higher elevations is observed with daily minimum temperatures increasing more than 1°C at 4600 m. Minimum daily temperatures shows more pronounced warming rates in the dry season than the wet at the highest elevation site. Consistent with this increased warming at elevation, we see a significantly decreasing trend in the monthly mean ground-level temperature lapse rate. Using the Weather Research and Forecasting Model, ERA 5 reanalysis data is downscaled to 1km resolution to compare the simulated lapse rates with our ground observations. There were also increasingly positive rates of change in dewpoint and relative humidity with height. Just as the temperature trends, the increase in humidity was most apparent at higher elevations, especially above 4500 m. Absolute humidity increases generally, with a greater rate at higher elevation Stations at lower elevations exhibited more daily and seasonal variations in humidity trends than temperature trends. The most evident increasing humidity trends are associated with the higher elevation sites during the wet season. Notable extremes are also recorded including unprecedented maximum temperatures during the 2023-24 hydrologic year.