A low-cost and low-weight sensor system for urban heat island surveys and education

CHRISTEN, ANDREAS; BAAD, FELIX; HEINZ, CHRISTEN; LAFRAMBOISE, AMY; LEE, JOSEPH; PICONE, NATASHA; REDEPENNING, DIRK

Braunschweig, Alemania

Conferencia; METTOOLS 2018; 2018

Technische Universität Braunschweig

The canopy layer urban heat island (CLUHI) is the most widely studied urban climate phenomenon. In particular, the intra-urban variability of the CLUHI has lately received significant attention due to climate change increasing the risk of heat stress in German cities. Experimental studies of the CLUHI use either simultaneously measured air temperatures from fixed stations, or employ mobiletraverses using thermometers traversing a city.The CLUHI is an excellent topic to stimulate undergraduate engagement in environmental meteorology, combining aspects of atmospheric observation technology and geospatial analysis in the context of a changing climate and urban adaptation measures. Here we present the development and application of a light, replicable, and ?low-cost? (?60) urban traverse system that can be easily assembled in undergraduate education projects. The systems can be ?mass deployed? on bikes (or cars) and simultaneously map geotagged air temperature and humidity as they move through cities and adjacent rural areas. We programmed25 Raspberry Pi Zero W microcontrollers (Raspberry Foundation) to collect data from digital lowcost thermometers / hygrometers (DHT22 / AM2302) and merged data with GPS location, altitude and speed (Adafruit Ultimate GPS Breakout V3). Sensors are housed in a reflective tube to provide a radiation shield. If cycling speed is ensured at > 8 km / h, sensors are sufficiently ventilated andprovide useable data to resolve air temperature values. Systems are powered using cell-phone charger battery banks and housed in bicycle accessory bags (Figure 1). Using wireless communication, data are transmitted and displayed on the operator?s smartphone.The contribution showcases our experience in undergraduate education with a fleet of 25 systems mapping simultaneously the nocturnal urban heat island of Freiburg. Prior to the traverse, we calibrated all sensors against a reference CS 215 (Campbell Scientific Inc.) and applied sensor specific corrections to match uncertainties in temperature and humidity readings. We classifiedFreiburg into different Local Climate Zones, and explored the influence of urban density and green fraction on nocturnal temperatures. We further observed influences of thermo-topographic airflow on the spatial structure of the CLUHI along the main drainage channels. Engaging undergraduate students in this project was rewarding to showcase data collection techniques in meteorology. The project introduced students to challenges of crowd-sourced data collection andgeospatial data visualization, and engaged them in approaching and addressing environmental meteorological problems.