Towards operational use of aircraft‐derived observations: a case study at London Heathrow airport

Abstract

Mode‐Selective Enhanced Surveillance (Mode‐S EHS) aircraft reports can be collected at a low cost and are readily available around busy airports. The new work presented here demonstrates that observations derived from Mode‐S EHS reports can be used to study the evolution of temperature inversions since the data have a high spatial and temporal frequency. This is illustrated by a case study centred around London Heathrow airport for the period January 4–5, 2015. Using Mode‐S EHS reports from multiple aircraft and after applying quality control criteria, vertical temperature profiles are constructed by aggregating these reports at discrete intervals between the surface and 3,000 m. To improve these derived temperatures, four smoothing methods using low‐pass filters are evaluated. The effect of smoothing reduces the variance in the aircraft derived temperature by approximately half. After smoothing, the temperature variance between the altitudes 3,000 and 1,000 m is 1–2 K; below 1,000 m, it is 2–4 K. Although the differences between the four smoothing methods are small, exponential smoothing is favoured because it uses all available Mode‐S EHS reports. The resulting vertical profiles may be useful in operational meteorology for identifying elevated temperature inversions above 1,000 m. However, below 1,000 m they are less useful because of the reduced precision of the reported Mach number. A better source of in situ temperature observations would be for aircraft to use the meteorological reporting function of their automatic dependent surveillance system.

Collecting and utilising crowdsourced data for numerical weather prediction: Propositions from the meeting held in Copenhagen, 4–5 December 2018

“…There are many potential benefits of such data, including the availability of large numbers of inexpensive observations, in areas where there are people but there may be few sources of scientific observation data. For example, (1) air traffic management reports have potential to provide observations of temperature inversions in the boundary layer (Mirza et al, , ). (2) In many locations around the world, the population has access to smartphones, but ground‐based scientific observations are sparse.…”

Editorial: The use of unconventional observations in numerical weather prediction

“…The application of the data smoothing results in vertical profiles that may be useful in operational meteorology, to study the evolution of temperature inversions above 1,000 m. However, the uncertainty in the smoothed temperature data is still too large for assimilation. The ModeS data discussed in Mirza et al (2019) provide the desired spatial and temporal resolutions required for convection-permitting NWP and, although the temperature data are not sufficiently precise, ModeS winds are now one of the opportunistic observations assimilated by operational NWP centres (e.g. Gustafsson et al, 2018;Milan et al, 2020).…”

“…The papers brought together in this virtual issue both highlight the need for very high resolution observations and show that unconventional data, either crowd-sourced or obtained from non-meteorological sources, can provide such information. The papers of Clark et al (2018), Mirza et al (2019), and Cornes et al (2020) all show that careful quality control and processing of unconventional data are important to ensure that biases and the uncertainty are reduced to a level sufficient for use in NWP. With appropriate quality control and processing, opportunistic observations can accurately represent small scale meteorological phenomena and are now beginning to be used in NWP to complement conventional observations.…”

“…The work of Mirza et al . (2019) performs an assessment of observations that can be derived from aircraft mode‐select enhanced tracking data (ModeS EHS reports). The authors show that application of quality control and an additional data smoothing must be applied to the high spatial and temporal resolution data to reduce the uncertainty in derived temperature observations to an acceptable level.…”

“…The ModeS data discussed in Mirza et al . (2019) provide the desired spatial and temporal resolutions required for convection‐permitting NWP and, although the temperature data are not sufficiently precise, ModeS winds are now one of the opportunistic observations assimilated by operational NWP centres (e.g. Gustafsson et al ., 2018; Milan et al ., 2020).…”